The ad tech glossary

309 terms, each answered in one sentence, then explained properly with an analogy and a worked example.

A

Ad inventory: Ad inventory is the total amount of advertising space a publisher has available to sell, usually counted in impressions across its ad slots, pages, apps or screens.
Ad network: An ad network is a company that aggregates ad space from many publishers and resells it to advertisers, usually in packaged bundles and often with its own pricing and targeting.
Ad operations (ad ops): Ad operations (ad ops) is the technical team and set of processes that set up, deliver, troubleshoot and report on ad campaigns, on either the publisher or the advertiser side.
Ad slot (ad unit): An ad slot (or ad unit) is a specific, defined place on a page, app screen or video stream where an ad can be shown, with its own size, format and rules.
Ad tech: Ad tech is the software and infrastructure that decides which ad appears where, buys and sells that ad space, delivers the ad, and measures what happened afterwards.
Advertiser: An advertiser is the company, organisation or person that pays to place ads in order to sell products, build a brand, recruit, or spread a message.
Agency: An agency is a company that plans, buys, creates or manages advertising on behalf of advertisers, in exchange for fees, commissions or a margin on the media it buys.

Campaign: A campaign is an organised set of ads with a shared goal, budget, audience and time period, run across one or more channels and measured against defined KPIs.
Conversion: A conversion is a valuable action that an advertiser wants people to take after seeing or clicking an ad, such as a purchase, sign-up, app install, call or form submission.
CPA (cost per acquisition): CPA (cost per acquisition) is the average advertising cost of getting one desired action, such as a sale, sign-up or app install, and also a model paying only for those actions.
CPC (cost per click): CPC (cost per click) is a pricing model where the advertiser pays only when someone clicks the ad, and also the average amount paid per click.
CPM (cost per mille): CPM (cost per mille) is the price an advertiser pays for one thousand ad impressions; "mille" is Latin for thousand.
CPV (cost per view): CPV (cost per view) is a video ad pricing model where the advertiser pays each time the video counts as viewed, according to the platform's definition of a view.
Creative: A creative is the actual ad content a person sees or hears, such as an image, video, audio spot, HTML5 animation or native text, delivered into an ad slot.
CTR (click-through rate): CTR (click-through rate) is the percentage of ad impressions that result in a click, calculated as clicks divided by impressions, multiplied by 100.

Direct-sold advertising: Direct-sold advertising is ad space sold by a publisher straight to an advertiser or agency through a negotiated deal, usually with a fixed price and guaranteed volume.

eCPM (effective CPM): eCPM (effective CPM) is the revenue or cost per thousand impressions calculated after the fact, which lets you compare ads sold on CPM, CPC, CPA or other models.

Fill rate: Fill rate is the percentage of ad requests that are actually filled with an ad, calculated as impressions served divided by ad requests, multiplied by 100.
Frequency capping: Frequency capping is a setting that limits how many times the same person, device or household sees a particular ad within a set period, such as three times per day.

Impression: An impression is one instance of an ad being served and counted as displayed to a user; it is the basic unit that most online advertising is bought and sold by.
Insertion order (IO): An insertion order (IO) is the signed contract between an advertiser or agency and a publisher or vendor, specifying what ads run, where, when, in what volume and at what price.

KPI: A KPI (key performance indicator) is the specific, measurable metric an advertiser or publisher chooses in advance to judge whether a campaign or business is succeeding.

Landing page: A landing page is the web page (or app screen) a person arrives at after clicking an ad, designed to convert that visitor into a buyer, sign-up or lead.
LUMAscape: A LUMAscape is a well-known industry map, published by investment bank LUMA Partners, that shows the hundreds of companies in ad tech and martech grouped by category.

Open web: The open web is the part of the internet outside the big closed platforms, such as independent websites, apps and streaming services, where ads are bought through shared, interoperable ad tech.

Pacing: Pacing is how evenly (or deliberately unevenly) a campaign spends its budget or delivers its impressions across its flight dates, so it neither runs out early nor under-delivers.
Programmatic advertising: Programmatic advertising is buying and selling ad space through automated software, usually one impression at a time, instead of through manual negotiations, phone calls and paper contracts.
Publisher: A publisher is any owner of content or a digital property, such as a website, app, streaming service, podcast or screen network, that earns money by selling ad space to advertisers.

Reach: Reach is the number (or percentage) of unique people or households who saw an ad at least once during a campaign, as opposed to the total number of impressions.
Remnant inventory: Remnant inventory is ad space a publisher has not sold through direct deals, which is then offered through programmatic channels, networks or house ads, usually at lower prices.
Retargeting: Retargeting is showing ads to people who have already interacted with a brand, for example by visiting its website, using its app or adding a product to a cart without buying.
ROAS (return on ad spend): ROAS (return on ad spend) is the revenue generated by advertising divided by the money spent on that advertising, usually shown as a ratio like 4:1 or 400%.

Sell-through rate: Sell-through rate is the percentage of a publisher's available inventory that has been sold, usually through direct or guaranteed deals, over a given period.

Targeting: Targeting is choosing which people, contexts, places, devices or times should see an ad, so that the budget is spent on the audiences most likely to respond.

Walled garden: A walled garden is a large platform, such as Google, Meta, Amazon or TikTok, that controls its own users, data, ad sales and measurement inside a closed ecosystem.