# Glossary

Essential AdTech terms defined. No jargon in the definitions—just clear explanations.

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## A

**Ad Exchange**
Marketplace where advertisers and publishers buy and sell ad inventory in real-time auctions. Think stock exchange, but for ads. Examples: Google Ad Exchange, OpenX, Rubicon Project.

**Ad Network**
Companies that aggregate ad inventory from multiple publishers and sell it to advertisers. The middleman between publishers and advertisers. Examples: Google Display Network, Taboola, Outbrain.

**Ad Server**
Technology that stores, manages, and serves ads to websites or apps. Tracks impressions, clicks, and basic performance. Examples: Google Ad Manager, Sizmek.

**Algorithmic Bidding**
Using machine learning to automatically adjust bids in real-time based on conversion probability. Also called automated bidding or smart bidding.

**Attribution**
The process of determining which ad touchpoints deserve credit for a conversion. Complex because users see multiple ads before converting.

**Audience Segmentation**
Dividing users into groups based on shared characteristics (demographics, behaviors, interests) for targeted advertising.

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## B

**Bid Request**
Information sent to advertisers during an RTB auction, including user data, page context, and ad placement details. Advertisers use this to decide whether to bid and how much.

**Bid Response**
Advertiser's reply to a bid request, containing their bid amount and the creative to show if they win.

**Bounce Rate**
Percentage of users who visit a site and leave without interacting. High bounce rates often indicate poor ad targeting or misleading creatives.

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## C

**CAC (Customer Acquisition Cost)**
Total cost to acquire a new customer, including all marketing and sales expenses. Critical metric for determining profitability.

**CDP (Customer Data Platform)**
System that collects and unifies customer data from multiple sources to create a single customer view. More focused on known customers than anonymous users (unlike DMPs).

**Click-Through Rate (CTR)**
Percentage of ad impressions that result in clicks. Formula: (Clicks ÷ Impressions) × 100. A 2% CTR means 2 out of 100 people who saw the ad clicked it.

**CMP (Consent Management Platform)**
Tool that manages user privacy consent, especially for GDPR and CCPA compliance. Handles cookie consent banners and tracks user preferences.

**Contextual Targeting**
Showing ads based on page content rather than user tracking. Making a comeback as cookies disappear. Example: shoe ads on running blogs.

**Conversion**
Desired action taken by a user (purchase, signup, download, etc.). What counts as a conversion varies by campaign goal.

**Conversion Rate**
Percentage of users who complete a desired action. Formula: (Conversions ÷ Visitors) × 100.

**Cookie**
Small text file stored on a user's device to track behavior across sessions. Third-party cookies (set by domains other than the one you're visiting) are being phased out.

**CPA (Cost Per Acquisition)**
How much you pay for each conversion. Formula: Total Ad Spend ÷ Conversions.

**CPC (Cost Per Click)**
How much you pay each time someone clicks your ad.

**CPM (Cost Per Mille)**
Cost per thousand impressions (mille = thousand in Latin). Standard pricing model for display advertising. If CPM is $5, you pay $5 for every 1,000 times your ad is shown.

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## D

**DCO (Dynamic Creative Optimization)**
Technology that automatically assembles personalized ad creatives in real-time based on user data. Same template, different content for different users.

**Demand-Side Platform (DSP)**
Software used by advertisers to buy ad inventory programmatically across multiple ad exchanges. Examples: Google Display & Video 360, The Trade Desk, Amazon DSP.

**DMP (Data Management Platform)**
System that collects, stores, and activates audience data for advertising. Primarily handles anonymous user data via cookies and device IDs.

**Dooh (Digital Out-of-Home)**
Digital advertising on billboards, transit displays, and other physical locations. Programmatically bought like online ads.

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## F

**First-Party Cookie**
Cookie set by the website you're visiting. Used for login sessions, preferences, shopping carts. Not being deprecated like third-party cookies.

**First-Party Data**
Data you collect directly from your customers (website visits, purchases, email interactions). The most valuable data type as third-party cookies disappear.

**Frequency Capping**
Limiting how many times a user sees the same ad. Prevents ad fatigue and wasted impressions.

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## G

**GDPR (General Data Protection Regulation)**
European privacy law that requires explicit user consent for data collection and gives users rights over their data. Applies globally if you serve EU users.

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## H

**Header Bidding**
Technology that lets publishers offer inventory to multiple ad exchanges simultaneously before calling their ad server. Increases competition and revenue compared to waterfall approach.

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## I

**Impression**
Single instance of an ad being displayed. Counted when the ad is served, though viewability standards vary.

**Interstitial**
Full-screen ad that appears between content pages. Often annoying but effective for mobile apps.

**ITP (Intelligent Tracking Prevention)**
Apple Safari's cookie-blocking technology that limits third-party tracking. Forces advertisers to adapt to privacy-first browsing.

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## L

**Lookalike Audience**
Group of users who share characteristics with your existing customers. Created using machine learning to find similar users for targeting.

**LTV (Lifetime Value)**
Total revenue a customer generates over their entire relationship with your company. Used to determine how much you can afford to spend on acquisition.

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## M

**Measurement Protocol**
API that allows sending event data directly to analytics platforms server-side instead of via browser JavaScript. Used in server-side tagging.

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## O

**Optimization**
Process of adjusting campaign parameters (bids, targeting, creatives) to improve performance. Can be manual or algorithmic.

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## P

**Pixel**
Tiny 1x1 image or JavaScript snippet that tracks user actions. When the pixel loads, it fires tracking data to an analytics or ad platform.

**PMP (Private Marketplace)**
Invitation-only ad exchange where premium publishers sell inventory to selected buyers at negotiated rates. More controlled than open exchanges.

**Programmatic Advertising**
Automated buying and selling of ad inventory using software and algorithms. Includes RTB, PMPs, and programmatic guaranteed deals.

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## R

**Retargeting**
Showing ads to users who previously visited your site but didn't convert. Reminds them to come back and complete the action.

**ROAS (Return on Ad Spend)**
Revenue generated per dollar spent on ads. Formula: Revenue ÷ Ad Spend. A 4:1 ROAS means you earn $4 for every $1 spent.

**RTB (Real-Time Bidding)**
Auction-based system where ad impressions are bought and sold in milliseconds as pages load. Core technology powering programmatic advertising.

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## S

**Second-Party Data**
Someone else's first-party data that they share with you directly. Essentially a partnership where both parties benefit from shared data.

**Server-Side Tagging**
Tracking approach where events are sent to your server first, then forwarded to ad platforms. Bypasses ad blockers and gives you more control than client-side tracking.

**SSP (Supply-Side Platform)**
Software used by publishers to manage and sell their ad inventory programmatically. The sell-side equivalent of a DSP. Examples: Google Ad Manager, Pubmatic, Magnite.

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## T

**Third-Party Cookie**
Cookie set by a domain other than the one you're visiting. Used for cross-site tracking. Being phased out by browsers due to privacy concerns.

**Third-Party Data**
Data purchased from external vendors who aggregate information from multiple sources. Becoming less valuable as cookies disappear.

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## U

**User Agent**
String sent by browsers identifying the device, operating system, and browser type. Used for device targeting and detection.

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## V

**Viewability**
Measure of whether an ad was actually seen by a user. IAB standard: 50% of pixels visible for at least 1 second (display) or 2 seconds (video).

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## W

**Waterfall**
Sequential ad serving approach where inventory is offered to buyers one at a time in priority order. Slower and less efficient than header bidding.

**Walled Garden**
Closed ecosystem where a platform controls user data, inventory, and measurement. Examples: Facebook, Google, Amazon. You can advertise there but don't own the data.

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## Z

**Zero-Party Data**
Information users intentionally share with you (survey responses, preferences, profile details). The most ethically collected data, though harder to obtain than passively tracked data.

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*This glossary covers core AdTech terminology. For deeper dives on any concept, refer to the relevant chapter in the book.*