Pay per click (PPC) refers to the online advertising payment model in which payment is based solely on qualifying click-throughs. In other words, advertisers pay the search engine each time someone clicks their ad.
PPC ads appear on the top premium position and along the right-side bar of the organic or natural listings on a search engine results page (SERP), and are labeled in various ways**. These paid ads are ranked on a SERP based on an auction model that determines which ads will display and in which positions.