A form of online advertising in which the advertiser pays when someone clicks on the advertisement.
Pay-per-click advertisements are usually placed automatically near search results, when someone has searched using a keyword or key phrase which the advertiser has specified.
For example, Google AdWords is a pay-per-click system which places advertisements as "sponsored links" next to search results. Advertisers bid for keywords, and the amount paid depends on factors such as the popularity of the keyword and the position in which the ad appears.
