Glossary

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A/B test - A type of experiment where one or more variations are tested against the control (original version) to see if the variations perform better with regard to an agreed upon conversion rate goal.
Ad exchange - Virtual marketplace where advertisers and publishers connect to buy and sell ad placements. Most often the transactions are done via real-time bidding auctions.
Ad hoc analysis - Type of exploratory analysis where the data is queried to answer one-off questions. This is in contrast to a more systematic analysis where popular questions are stored as queries that can be asked again and again as the dataset changes.
Advertiser - Advertisers have products, services, and brands that they want to promote through digital ads. They participate in auctions hoping to get their ads to consumers in relevant contexts around the web.
API - Strictly speaking application programming interfaces are methods and protocols in a piece of software that allow other sources to communicate with this software. More broadly they are used to describe any functions and methods that operate how the software works.
Asynchronous - When a resource is loaded asynchronously, the web browser does not need to wait for its download to complete. Instead, the browser continues the render process until the resource has been downloaded, at which point the browser will start rendering it.

Backlog - List of items that are waiting to be worked on by developers.
Bounce - If a user “bounces”, it typically means they leave the site or app without performing any meaningful actions. Bounces are considered the antithesis to “engagement”. A user who bounces has limited or no engagement with the site or app.
Browser engine - The core software component of any web browser. Its most important task is to convert resources loaded from web servers into the dynamic representation of the web page.
Business logic layer - The business logic layer is what defines how interactive elements such as forms, buttons, and links work. It also includes dynamic actions such as content that is loaded only once the user scrolls to the bottom of the visible page.

Cache - Caches are temporary storage mechanisms for frequently accessed things such as domain name queries, images, even entire web pages. Their purpose is to make the web faster.
California Consumer Privacy Act - A state satute in California, which expands California’s consumer privacy laws and introduces many additional user data protection and privacy measures into California’s legislation.
Call-to-action - A website or app element that invites the user to perform some action that is beneficial to the business. A typical example is a button the user can click to subscribe to a newsletter.
Click identifier - Many advertising platforms add identifiers to link addresses that indicate the click originated from the advertising platform. These click identifiers can be used by advertisers to link activities on a website with activities on the advertising platform.
Click-through rate - The ratio of users who click on something (usually a link) to the number of total users who saw the clicked element or its context (a page, email, or ad, for example).
Client - A machine connected to the internet that sends requests to a server. A web browser would be a typical example of a client, as it sends requests to web servers.
Consent - Data protection laws often defer to positive consent for collecting or processing data from the user. Requesting consent usually involves a consent banner or a consent pop-up where the user is asked whether the site or app can collect data from them.
Content Distribution Network - A collection of web servers designed to serve files and resources to websites. Images and JavaScript libraries are often downloaded from dedicated CDNs.
Conversion rate - The ratio of conversion events to visitors or sessions. A high conversion rate usually means that your visitors are performing actions that are beneficial to your business.
Cookie - Cookies are a way to persist information on the web from one page to the next and from one browsing session to the next. They are small bits of information always stored on a specific domain, and they can be set to expire (self-delete) after a given amount of time.
Core Web Vitals - A set of metrics that measure actual user experience for loading performance, interactivity, and visual stability of a web page.
Crawler - A machine that downloads and parses content on the web. It follows links to find additional content to fetch. Search engine crawlers use the parsed information to build the search engine index.
CRO - Conversion rate optimization refers to running tests and experiments with the purpose of improving the likelihood of conversion for visitors to your sites and apps.
Cross-site tracking - Tracking that collects data from users as they visit different, unrelated sites on the web. Usually requires third-party cookies to work.
CSS - Cascading Stylesheets, or CSS, is a web technology that describes how the web page should look like and, up to a certain point, respond to interactions. If the HTML document defines the content, then CSS describes how that content should be structured, aligned, and painted in the browser.
Customer Relationship Management - Software for managing all your organization’s relationships and interactions with customers and potential customers.

Data architecture - How data is structured, stored, and utilized within an organization. It’s a collection of data models, schemas, data flow maps, and governance instructions.
Data breach - A security incident that results in unauthorized access to confidential information.
Data broker - Data brokers sell additional information about consumers to advertisers and publishers. They usually hold huge swaths of data about users’ browsing history and interests, and this data is then traded to (ideally) improve the relevance of ads and ad placements across the board.
Data controller - A data controller determines the purposes and means of processing personal data. They decide the “how” and “why” of a data processing operation.
Data infrastructure - The physical components, services, and mechanisms that service an organization’s data practices.
Data lake - Collection of raw data from different sources in their native formats. Schemas are not applied until the data lake is queried.
Data Layer - A globally available JavaScript structure on the web page designed to pass information between the web page and the tag management system.
Data management platform - Advertisers use DMPs to upload additional information about their consumers and potential target audiences. This information can be used to add further granularity to the cohorts that should be targeted with the advertiser’s ads.
Data minimization - A principle by which only the minimum amount of data is collected to satisfy the purpose for which it was collected.
Data processor - The data processor processes personal data only on behalf of the controller.
Data protection - In the context of regulation, data protection is the process of safeguarding any data relating to an identified or identifiable natural person.
Data security - The process of protecting digital data throughout its entire life cycle from corruption, theft, or unauthorized access.
Data subject - An identified or identifiable natural person whose personal data is processed by a controller or processor.
Data subject access request - Data subject access requests, or DSARs, are formal requests to organizations by individuals who want to access their (personal) data that is processed and stored by the organization. The purpose of such a request is to ensure that any personal data processing that takes place is done lawfully.
Data warehouse - Data warehouse is a repository of data collected by an organization from different sources. The data can then be transformed within the data warehouse before being made available for querying against.
Database - Structured storage for data that usually serves a singular purpose. For example, a company’s financial records would be stored in a database.
Demand-side platform - Advertisers can use DSPs to negotiate with different auctions and ad exchanges automatically. The advertiser would create their ad campaign in the DSP and then have the DSP determine which auctions to participate in.
Denormalize - Denormalization in data schemas means that redundancy is intentionally introduced by joining data from multiple tables. The same bits of information can appear multiple times in the data warehouse. This optimizes the data for read-heavy operations, such as that required by data analytics processes.
Descriptive - A descriptive schema is built so that the data is structured to suit the needs and requirements of the company managing the website rather than the marketing vendors the company works with.
Developer tools - Browsers offer comprehensive toolkits for debugging many different aspects of the modern web experience. Learning these tools is one of the most important things for a technical marketer.
DNS - The domain name system (or DNS) is the address book of the internet. It maps all (existing) internet domain names to a server or some other destination.
Document Object Model - The dynamic, JavaScript-based representation of the page HTML and styles. When you look at a web page, you are actually looking at the visual layer of the DOM.
Domain - Domain names are stored in the domain name system (DNS) and are used to map a human-readable name (such as www.teamsimmer.com) to a web server.

E-commerce - E-commerce represents the industry of online sales. E-commerce covers online transactions that happen on the web, among other things.
Edge cache - Services like Cloudflare can be used to cache frequently loaded resources from the “edge” of the network, as close to the users as possible, instead of having to fetch it across the web. This can result in amazing performance boosts for HTTP requests and resource loads.
Encryption - When information is encrypted, it is obfuscated in such a way that no one without the encryption key should be able to determine what the data actually comprises.
ePrivacy Directive - A directive in the European Union that deals with the confidentiality of information and treatment of traffic data, spam, and access to device storage (such as through browser cookies).
Event-driven - An event-driven Data Layer is one that both feeds data to a TMS and triggers the tags within the TMS. A TMS would attach “listeners” to an event-driven Data Layer, so that it can react to new data that is added to the Data Layer.

Flicker - Also known as “flash of original content”. Sometimes users see a quick flicker of the original version of an element before the change is applied to the element based on the user’s group assignment in the test.
Fold - The “fold” means the visible part of the page when a visitor loads it in the web browser. Items that are “below the fold” usually require the user to scroll to them.
Fragment - A URL component that solely exists in the web browser – it is not communicated to the web server when requests are dispatched. Usually fragments are used to navigate directly to certain places on a content page.

General Data Protection Regulation - General Data Protection Regulation is a set of data protection laws and rules that apply to data subjects within Europe. Its purpose is to give individuals vast protections for any personal data that is collected and processed on their behalf.
Geolocation - The act of geographically locating the user on the globe. In the context of an analytics system, geolocation is usually done with a reverse lookup of the user’s IP address, as all IP addresses have a geolocation associated with them.
Git - Probably the best-known version control system in the world. Git allows multiple people to work on the same code without disrupting each other’s work.

Hostname - The URL component that contains the domain name (and optional port) of the web server. The hostname can also be an IP address.
HTML - HyperText Markup Language (HTML) is used to describe how web documents should be rendered by the web browser. When you navigate to a web page, the web server hosting that page serves your browser an HTML source file that is then rendered into the visible and interactive web page.
HTTP request - HyperText Transfer Protocol is the main communication method of the World Wide Web. When clients send requests to web browsers, they are sent using HTTP. The purpose of the request is to fetch data from the web server.
Hyperlink - Hyperlinks, or just links, are elements on the web page that redirect the user to another page when clicked.
Hypothesis - An assumption based on research that you want to prove or reject with experimentation. Minimally, it needs to include what you intend to change, what the expected outcome is, and what your rationale for the hypothesis is.

Impression - When something is viewed, it generates an impression. Programmatic advertising is measured and sold in chunks of impressions, i.e. potential views of any given ad.
IP address - An Internet Protocol address is attached to every single machine connected to a network, including the public internet.

JavaScript - JavaScript is the main language of the dynamic web. The web browser renders the HTML source file into a dynamic document that can be interacted with using JavaScript.
JSON - JavaScript Object Notation is a popular format for encoding JavaScript objects as strings. It’s usually used with HTTP network requests, but can be used for other purposes like structured data, too.

Key-value pair - Key-value pair is a generic term used to describe the contents of an object. An object is a data structure that can have zero or more key-value pairs. Each object can have just one of any given key, and the key always needs to point to some value.

Landing page - In digital marketing, a landing page refers to a page on a website which the marketing campaign links to. Landing pages are created for ads and newsletter links, for example, but they can be used more generally with any marketing campaign (even non-digital ones).
Latency - Another word for delay. The higher the latency, the longer the delay between the action and the consequence.
Lazy loading - Lazily loaded content is loaded dynamically, usually when the browser user scrolls to the content so that it appears in the viewport. Lazy loading helps make the initial page load process lighter and faster.
Library - Another word for a file that contains code which can be utilized by downloading the library into the application. For example, when the web browser loads JavaScript files from vendors, those are frequently called libraries.
Log storage - In networking, log storage contains an entry for each network request received by the server. The log entry typically includes metadata such as the request URL, the origin of the request, the timestamp of the request, and the IP address of the request source.

Markup - In web technologies, markup is the process of “marking up” a document with tags or similar codes. This process can be formalized in languages like HTML or XML.
Metadata - Metadata is additional data about the data itself. For example, in an analytics system the “event” describes that action the user took, and metadata about the event could contain additional information about the user or the event itself.
Microdata - A specification for nesting structured data within HTML content.
Minimum detectable effect - The smallest real change to the baseline conversion rate that you want the experiment to detect.
Multivariate test - An experiment where more than one variable is tested at the same time. The results are analyzed using combinations of different variables to see which is the strongest one.

Naming convention - A set of instructions for how to name keys within the Data Layer. For example, a naming convention could dictate that all keys need to be in snake_case rather than in camelCase.
NPS - A survey type that asks “how likely are you to recommend us to others?”. The scale is 0 to 10, with 9 and 10 considered “promoters”, 7 and 8 as “passives”, and 0 through 6 as “detractors”.

Object - Object is a JavaScript construct that comprises key-value pairs. The Data Layer (a type of object itself) typically consumes objects of data.
Organic - In digital marketing, the word “organic” is often used with traffic from search engines, excluding those that came from a search ad click.

Partition - Partition means to logically split data in some way. A typical partitioning method is by date, where data is stored in partitions by date of ingestion. Partition can also reference other aspects of the digital world, such as when browser storage is partitioned (stored separately) by website.
Payload - In an analytics system, the payload is used to describe the data in the request address or the request body, specifically designed to be associated with the analytics system’s schemas at processing time.
Pixel - Pixels are the smallest units that make up the visible part of a web page.
Prescriptive - A prescriptive approach to Data Layer design is one where a vendor dictates the naming conventions and the structures of the Data Layer. Usually the purpose is to allow the vendor to directly integrate with the Data Layer rather than having to go through a TMS or to have the data transformed with variables.
Presentation layer - The presentation layer of a web page is built with HTML and CSS, although JavaScript can also be used to dynamically change elements of this layer. It’s the visible content of the web page, including the structure of the visible content, such as the grid layout or the responsive design of the page.
Privacy by Design - An approach where data protection and privacy measures are baked into the technological design of an app or service from the very beginning.
Protocol - The HTTPS or HTTP part of a URL is the protocol that establishes whether the request should be sent securely (HTTPS) or insecurely (HTTP). Other protocols you might see on the web include mailto (for sending emails) and ftp (for transferring files).
Publisher - In programmatic advertising, the publisher owns a website, app, or other digital property, and they are willing to sell ad placements to advertisers. When consumers visit the publisher’s site, for example, they might see ads from other websites in these placements.

Query string - Query strings can encode additional information for web server using key-value pairs that are separated with the ampersand (&).

Real-time - Real-time analysis refers to analysis of data that is currently being collected. For example, a publishing media might use real-time data to see how many people are consuming content at any given time. “Real-time” is never really real-time – there’s always a latency of at least some milliseconds, usually seconds or even minutes.
Redirect test - An experiment where instead of showing different variations of a section of a page, users are distributed to different versions of the entire page instead. Redirect tests are useful when testing large, page-wide changes.
Relational - Data is organized relationally when it’s distributed across columns, rows, and tables in such a way that entries are linked together using keys. For example, a user can be represented by a user_id both in a table of purchases (who made the purchase) and in a table of users (who is the user).
Render - Rendering happens when the web browser starts to convert the HTML document and its associated resources into the dynamic document the user sees and interacts with when visiting a web page.
Representative sample - Some analytics tools respond to queries with representative samples of the data rather than all the data that matches the query. It’s often faster for the tool to generate a sample than to fetch all the available data. The sample is considered representative when it can be generalized to the entire dataset, within a certain […]
Request header - A network request comprises (at least) a request address, headers, and an optional body. The headers contain metadata about the request, such as the user’s IP address and information about the device and browser they are using.
Retargeting - When users see ads about sites they have previously visited or products they have previously engaged with, they are being retargeted by these ad campaigns.
RTB - Real-time bidding is a fully automated auction process for buying and selling digital ad impressions. Both advertisers and publishers use it to optimize ad placements by targeting specific users in real-time.

Sample size - The number of visitors your experiment needs in order to have enough of a chance to reach a statistically significant result when there is an effect to be detected.
Schema - An analytics system uses schemas to parse, validate, and store events ingested by the collector. The schema dictates what a valid event looks like, what data types are accepted by the system, and what values are required in all incoming events. Schema can also be used to describe the structure of other things, such as […]
Schema.org - A collaborative repository of schemas for structured data on the Internet.
Scrape - Some tracker libraries can be configured to scrape information from the page. This means that they use JavaScript to access information on the page rather than going through, for example, a Data Layer. Scraping can be hazardous if done autonomically, because analytics systems can end up inadvertently scraping credit card numbers of other sensitive data.
SDK - Software Development Kit. Mobile apps use SDKs to run most of their functionality. SDKs are analogous to JavaScript libraries on web pages.
Search engine optimization - SEO focuses on improving a website’s visibility and reach for users who perform relevant queries in a search engine.
Segmentation - When data is grouped by property, attribute, or value, it is segmented. When building audiences for ads, for example, you need to choose for which user segments to target the ads.
SERP - The search engine results page is where you’ll see a listing of sites and ads once you run a query in a search engine.
Single-page app - A type of website where only the first page is loaded through a regular navigation action. The rest of the navigation pages are loaded dynamically with JavaScript without creating an actual navigation event in the browser.
SQL - Structured Query Language (SQL) is a standardized, domain-specific language designed for accessing and manipulating data. It is particularly powerful with structured and relational datasets.
Statistical significance - The likelihood of a test result to be caused by something other than pure chance.
Structured data - Structured data is a semantic layer on a website, explaining what the website is about and what different entities on the page are. This information is usually provided for bots and crawlers to consume.
Style guide - Documentation that explains how the organization approaches the styling of things. Typical topics in a style guide include code styling (syntax and semantics) and UI / design element styling.
Supply-side platform - Publishers can use SSPs to manage their ad placements and available ad spaces. By managing inventory in an SSP, the publisher can access different auctions, ad exchanges, and advertisers automatically.

T-shaped - A skill profile where the practitioner has deep knowledge in a specific area (the vertical bar) and superficial knowledge about other, related areas (the horizontal bar).
Tag - Normally, tag references an HTML element (or node). In a marketing context, tags are used to denote HTML elements and JavaScript snippets specifically designed for collecting data to marketing vendors.
Tag Management System - TMS are software designed to create, manage, and deploy tags on web pages. They offer a user interface for managing the marketing tags on any given page.
Technical debt - Generally technical debt describes design patterns that will cause problems in the future if they’re not appropriately fixed or maintained over time. Typical example of technical debt is a patch or a workaround that was supposed to be temporary but that isn’t actually updated when the underlying problem goes away.
Test coverage - How much of the code is “covered” by tests. Testing suites can quickly compute which lines of code would be accessed by any given test, and you can then see if there are important parts of the code that have no tests written for them yet.
The build - Generally used to denote a version of the app or software project that is waiting for release.
Top-level domain - The most generic part of the domain name in the hostname component of the URL. The top-level domain can be, for example, a country name (.fi, .se, .co.uk), a generic name (.com, .net, .org), or something more adventurous (.baby, .farm, .holiday).
Tracker - Software that typically runs in the user’s web browser or device, designed to collect data from the user to a server.
Trigger - A tag management system uses triggers (also known as rules) as activation instructions for tags. When trigger conditions are satisfied, any tags that reference that trigger can fire.

Unix timestamp - Computer time is often measured in Unix time. It’s a standardized format, describing the number of seconds (or milliseconds, or microseconds, or even nanoseconds) since 00:00:00 (UTC), January 1st, 1970.
URL - Universal Resource Locator, the main method of encoding internet addresses for web browsers to send requests to.
URL origin - The part of the URL that comprises the protocol, hostname, and optional port. For example, https://handbook.teamsimmer.com is the URL origin of this site.

Variable - Variables are (usually small) pieces of code run in a TMS to fetch dynamic values for tags when they fire. A defining feature of variables is that they are re-evaluated whenever a tag fires. For example, if a variable fetches the exact time when a tag fired, it’s important that it doesn’t use the same, […]
Variant - In experimentation, variants are different versions of the variable that is the target of the experiment. Any visitor included in the experiment would (ideally) be exposed to a single variant of the variable for the duration of the test.
Version control - A process of tracking and managing changes to code. Popular versioning involves “branches”, where the main branch is separated from work-in-progress branches.
Viewport - The area of the web page or app visible to the user at any given time. It is constrained by the size of the browser window and the resolution of the user’s device.

Walled garden - Some companies are big enough to handle all aspects of the ad platform themselves, from managing ad campaigns, to creating and populating target segments, to serving the ads as the publisher. These companies are known as walled gardens.
Web server - A machine connected to the World Wide Web, which is purpose-built to respond to HTTP requests from clients and for sending resources in response.
Web standard - A set of agreed principles for how web browsers should render web content and how that web content can be interacted with.