It refers to the search engine where the rankings are allocated based on the bid amount placed.

Among different things an advertiser has to supply to pay per click search engine include: keywords, listing and bids. When a search is initiated the first listing to be displayed will be the one that has the highest bid on that particular keyword. The ranking thus displayed from highest to lowest bids. The keyword with highest rankings generally garners more traffic than the rest.For a marketing point of view, it is very important to determine which of the pay per click search engines will generate more quantity and quality of visitors for a given category of product. It will then be easier to take further actions based on facts.