Pay Per Click is an advertising model in which the advertisers only pay for each click to their Web site. The ads are served on the web, based on a defined set of keywords or themes relating to the advertiser’s business. Pay Per Click usually requires you to bid on key words or phrases of your choice. The highest bid gets the top ranking on the search results and then you pay the bid amount every time someone clicks on your link.
Some programs such as Yahoo! Sitematch charge a flat rate per click, so as with free listing engines, you'll still need to ensure that you have carried out the necessary search engine optimization processes in order to gain good rankings. Also, you can spend thousands on clicks, but if the page that visitors land on isn't up to scratch, your money will be wasted - those clicks simply won't convert. Learn more about creating effective landing pages.