Sponsored listings

Sponsored listings is a fee-based service that allows commercial web sites to receive enhanced placement in certain categories in the search engine's directory or other websites. The commercial website creates its own ads and chooses the keywords related to their business and are featured in a "Sponsored" module within the appropriate category. They are also highlighted in the regular alphabetic list of sites.
Usually the advertiser bids in an auction based marketplace for search terms to get his customized ads displayed to users on other web properties, which could be the service providers own website (such as a search engine) or websites of partners of the provider. Partner websites could be other search engines or any other website, which is usually referred to as content network.

“Source: Small Business.yahoo.com & Wikipedia ”