The ad tech glossary: every term you'll actually encounter, explained

Ad tech has a vocabulary problem. Every conversation is dense with acronyms, and most explanations define one acronym using three others. This glossary fixes that: plain-English definitions of the terms you’ll actually encounter, grouped by area, with a link to a full guide wherever we’ve written one.

Bookmark it. New to all this? Start with the guided learning path instead.

The players

SSP (supply-side platform) — the publisher’s technology for selling impressions automatically. → SSP vs DSP vs ad exchange

DSP (demand-side platform) — the advertiser’s technology for buying impressions. → SSP vs DSP vs ad exchange

Ad exchange — the marketplace where SSPs and DSPs meet and the auction runs. → Ad networks vs exchanges

Ad network — an older model that aggregates inventory and resells it in bundles rather than per impression. → Ad networks vs exchanges

Ad server — the system that stores creatives, decides which ad wins a slot, delivers it, and counts the result. → Ad servers explained

Publisher — the owner of the content and the ad space. Advertiser — the buyer of that space.

Curator — an entity that assembles vetted inventory (often with data) into ready-to-buy packages. → Curation explained

Walled garden — a large platform controlling its own inventory, data, and measurement in a closed ecosystem. → Walled gardens explained

The auction

RTB (real-time bidding) — auctioning a single impression live, in ~100ms, as a page loads. → OpenRTB & RTB explained

OpenRTB — the shared IAB specification that lets any SSP talk to any DSP. → OpenRTB & RTB explained

Bid request — the structured description of an impression sent to buyers. Bid response — the buyer’s bid.

First-price auction — the winner pays exactly what they bid (today’s norm). Second-price auction — the winner pays just above the runner-up. → First-price vs second-price

Bid shading — a buyer bidding below true value to avoid overpaying in a first-price auction. → Bid shading explained

Floor price — the minimum bid an impression will accept. Dynamic floor — one computed per impression in real time. → Dynamic floor pricing

Header bidding — offering an impression to many demand sources simultaneously before the ad server decides. → Header bidding explained

Prebid — the open-source framework most header bidding runs on. → Prebid explained

Timeout — how long the auction waits for bids before giving up. → Auction timeouts & latency

Waterfall — the legacy model of asking demand sources one at a time, in a fixed order.

Deals & buying models

Open exchange — the fully open auction, available to any buyer. PMP (private marketplace) — an invite-only auction with a Deal ID. Preferred deal — one buyer, fixed price, no volume commitment. PG (programmatic guaranteed) — fixed price and guaranteed volume. → Programmatic deal types

Deal ID — the identifier that connects a buyer to a specific negotiated deal.

Upfront / scatter — TV’s annual advance marketplace, and the later spot market. → Linear TV explained

Pricing & yield

CPM — cost per thousand impressions. CPC — cost per click. CPA — cost per action. CPV — cost per view. → CPM vs CPC vs CPA

eCPM (effective CPM) — normalized earnings per thousand impressions, letting you compare any pricing model. → Understanding eCPM

Fill rate — the share of ad requests that returned a paid ad. → Fill rate explained

Yield optimization — maximizing sustainable revenue per impression. → Yield optimization

Ad tech tax / take rate — the combined cut taken by intermediaries between advertiser and publisher. → The ad tech tax

Supply chain & quality

ads.txt / app-ads.txt — public files where a publisher lists who’s authorized to sell its inventory. sellers.json — the exchange’s public file identifying its sellers. → ads.txt & sellers.json

SupplyChain object (schain) — the bid-request field naming every hop the impression passed through. → SupplyChain 1.1

SPO (supply path optimization) — concentrating spend on the shortest, cleanest routes to inventory. → SPO explained

IVT (invalid traffic) — impressions from bots or fraud rather than genuine humans. → The state of ad fraud

Domain spoofing — passing off junk inventory as a premium site. SSAI spoofing — faking devices in server-stitched streams.

MFA (made-for-advertising) — sites built to harvest ad revenue rather than serve readers. → MFA explained

Malvertising — using the ad supply chain to deliver malware or scams. → Malvertising explained

Brand safety / brand suitability — keeping ads off harmful content, and off content wrong for a specific brand. → Brand safety & suitability

Traffic shaping — an exchange filtering which bid requests it forwards, cutting waste. → Traffic shaping explained

Identity, data & privacy

First-party data — data you collect directly from your own audience, with consent. Second-party — someone else’s first-party data, shared. Third-party — aggregated and sold by brokers. → First-party data

Third-party cookie — the cross-site identifier that powered tracking, now in decline. → Privacy Sandbox state of play

Cookie syncing — the handshake letting two platforms agree their IDs refer to the same user. → Cookie syncing

Universal ID — a shared identifier meant to replace the third-party cookie. Identity graph — the map linking one person’s many devices. → Identity resolution · Cross-device tracking

Deterministic vs probabilistic — identity from confirmed logins vs. inferred from patterns.

DMP — organizes anonymous third-party segments. CDP — unifies known first-party customer profiles. → DMP vs CDP

Data clean room — a neutral environment where two parties match data without exposing raw records. → Data clean rooms

CMP (consent management platform) — captures user privacy choices and signals them downstream. TCF — the IAB framework that carries consent through the chain. → Consent management

SDA (seller-defined audiences) — publisher-declared audience cohorts passed in the bid request, no user ID required. → Seller-defined audiences

Targeting & creative

Contextual targeting — matching ads to page content rather than user identity. → Contextual advertising

Behavioral targeting — targeting based on a user’s past browsing and purchases.

Retargeting / remarketing — reaching people who already engaged with a brand. → Retargeting explained

Lookalike audience — new people who statistically resemble a seed audience. → Audience targeting types

DCO (dynamic creative optimization) — assembling the best creative combination per impression. → DCO explained

Native advertising — ads matching the form and function of surrounding content. → Native advertising

Frequency capping — limiting how often one person sees the same ad. → Frequency capping

Video, CTV & other channels

CTV — the internet-connected TV device. OTT — video delivered over the internet. FAST — free ad-supported streaming channels. AVOD — ad-supported on-demand. → CTV explained · FAST channels

SSAI (server-side ad insertion) — stitching ads into the video stream server-side for seamless playback. → SSAI explained

VAST — the standard letting any player request and track a video ad. VPAID — its deprecated interactive extension. VMAP — schedules ad breaks. OMID — open measurement. → VAST & VPAID

Ad pod — a set of ad slots within one CTV break. → Ad pods explained

Linear TV — scheduled broadcast/cable television. GRP — gross rating points, TV’s audience currency. → Linear TV explained

DOOH — digital out-of-home screens. → DOOH explained

Retail media network (RMN) — a retailer selling ads against its own shopper data. → Retail media

In-app — advertising inside mobile apps, via SDK and mediation. → In-app advertising

In-game — advertising inside game environments. → In-game advertising

Measurement

Viewability — whether an ad met the MRC threshold of 50% of pixels for 1 second (2 for video). → Ad viewability

Attention metrics — models estimating whether an ad was genuinely noticed. → Attention metrics

VCR (video completion rate) / CPCV — how often video plays to the end, and cost per completed view. → Video ad metrics

Attribution — crediting touchpoints for a conversion. Incrementality / lift — the conversions advertising actually caused. → Incrementality explained

MMM (media mix modeling) — statistically estimating each channel’s contribution without tracking individuals. → MMM explained

Ad ops (ad operations) — the people and processes that traffic, QA, and troubleshoot campaigns. → Ad operations

---

Lumorrow is an AI-native exchange that evaluates supply quality and sets floors in real time, pre-auction. See how the platform works → · New here? Start with the learning path →