Paying for ad placement on the results page of a Web search engine. Also called "paid search," advertisers typically bid for higher placement of their ad on the page. Ads are matched to the words being searched; for example, a publisher of a computer dictionary might use keywords such as "computer terms" and "computer definitions." If the user searches for these words, a text link or banner ad is displayed at the top or side of the search results page. If the user clicks the ad, the search engine charges the advertiser for the click-through.Keyword advertising is also deployed on regular websites, whereby ads are delivered based on keywords embedded in the Web pages. See affiliate program, Overture, Google AdSense and Google AdWords.