The model inverts the economics of older advertising. A newspaper or a banner is paid for by exposure; a search ad costs nothing until a person chooses it. The advertiser picks keywords, the queries it wants to appear for, writes the ad, sets a bid and a daily budget, and points the ad at a landing page. Each time someone searches, the platform holds an auction among every advertiser whose keyword matches, orders the ads and charges the winners when they are clicked. The same mechanism prices ads on shopping results, on video and across display networks, which is why the Google Ads curriculum splits into Search, Display, video, shopping and measurement certifications.
The bid is only part of the auction. Google scores every keyword and ad pairing with a Quality Score from 1 to 10 built from three components, expected clickthrough rate, ad relevance and landing page experience, and the help page is explicit that the score itself is a diagnostic rather than an auction input: the same signals, estimated live for each search, decide where the ad shows and what the click costs. A relevant ad on a fast, matching landing page pays less per click than a poor one bidding the same amount. That is the lever a practitioner works: the account structure, the match between query and ad, and the page after the click, before the bid.
| Quality Score component | What it measures | What moves it |
|---|---|---|
| Expected clickthrough rate | How likely the ad is to be clicked when shown for the keyword | Ad copy that matches the query; keywords grouped tightly |
| Ad relevance | How closely the ad matches the intent behind the search | One theme per ad group; the keyword in the headline |
| Landing page experience | How useful and usable the page after the click is | The page answers the query, loads fast, works on a phone |
- Keywords and match types decide which searches trigger the ad; keyword research comes before the first bid.
- Conversion tracking turns clicks into outcomes; without it the account optimises for traffic and the bill grows.
- Negative keywords stop the ad showing for searches that cost clicks and never convert.
- Bidding moves from manual cost per click to automated strategies once the account has enough conversions for the platform to learn from.
Paid search sits beside SEO on the same results page, and the two are run by different people with different clocks. The paid result appears when the budget starts and disappears when it stops; the organic result takes months to earn and continues afterwards. Most businesses run both, using the paid data on which queries convert to decide which pages are worth the organic effort. The paid search and display courses teach the account mechanics; the arithmetic of margin against cost per acquisition is what decides whether the channel is kept.