Advertising glossary

30 terms, each answered in its first sentence, with what it means when the budget is small.

Ad fatigue: Ad fatigue is the drop in response when the same audience has seen the same ad too many times.
Ad frequency: Ad frequency is the average number of times each person in an audience has seen an ad: impressions divided by reach.
Ad impression: An ad impression is counted each time an ad is loaded to be shown on a screen, whether or not anyone sees it.
Bid ceiling: A bid ceiling is the highest price an auction will accept, which caps what any buyer can pay for a placement.
Bidstream data: Bidstream data is the information sent out in real-time bidding requests: the page, the device, the location and visitor identifiers.
Contextual advertising: Contextual advertising places ads by the content of the page, not by tracking the person viewing it.
Conversion rate: Conversion rate is the share of visitors who complete the action you want, such as signing up or buying.
CPA (cost per acquisition): CPA is what it costs in advertising to win one customer or conversion: total spend divided by conversions.
CPC (cost per click): CPC is the price an advertiser pays each time someone clicks an ad, the usual model for search advertising.
CPM (cost per mille): CPM is the price an advertiser pays for one thousand ad impressions, whether or not anyone clicks.
CTR (click-through rate): Click-through rate is the share of people who saw an ad and clicked it: clicks divided by impressions.
eCPM (effective CPM): eCPM is what an ad placement earned or cost per thousand impressions, whatever way it was actually priced.
First-price auction: In a first-price auction the winning bidder pays exactly what it bid, rather than a price set by the runner-up.
Flat-fee advertising: Flat-fee advertising is a placement sold at one fixed price, such as a newsletter sponsorship or a week-long site banner.
Header bidding: Header bidding lets a publisher offer each impression to several ad exchanges at once before calling its ad server.
Invalid traffic (IVT): Invalid traffic is ad impressions and clicks that do not come from genuine human interest, from bots to accidental clicks.
Last-click attribution: Last-click attribution credits a sale entirely to the final ad or link a customer clicked before buying.
Media kit: A media kit is the document a publisher gives advertisers: who the audience is, how large and engaged, and what placements cost.
Nofollow: Nofollow, rel="nofollow", is a link attribute asking search engines not to treat a link as a vote for the page it points to.
Programmatic advertising: Programmatic advertising is the automated buying and selling of ad space by software, usually through real-time auctions.
Rate card: A rate card is a publisher's published list of advertising prices: what each placement costs and what it includes.
Real-time bidding (RTB): Real-time bidding is the auction that sells a single ad impression to the highest bidder while the page is still loading.
Retargeting: Retargeting shows ads to people who have already visited your site or used your app.
ROAS (return on ad spend): ROAS is the revenue an ad campaign brings in divided by what it cost, written as a multiple such as 3×.
Second-price auction: In a second-price auction the highest bidder wins but pays just above the second-highest bid.
Single-source attribution: Single-source attribution gives all the credit for a conversion to one touchpoint, usually the first or the last.
Sponsored link attribute: The sponsored link attribute, rel="sponsored", marks a link as paid so search engines do not count it as an endorsement.
Statistical significance: A test result is statistically significant when a difference that large would rarely appear by chance alone.
Time-boxed ad slot: A time-boxed ad slot is a placement sold for a fixed window of time, such as twelve hours, rather than per impression or click.
Viewable impression: A viewable impression is a display ad with at least half its pixels on screen for one continuous second.