Ad network: An advertising company that brokers deals between online publishers and advertisers. Bigger ad networks aggregate sites into general categories so that they can offer advertisers targeted markets. Ad networks are responsible for selling and serving the majority of Internet advertising.
Ad networks sell advertising space for online ads. This space can be on a website, RSS feed, blog, instant messaging or forum space. Where an ad runs and what sort of control an advertiser has over the ad is determined through negotiation with an ad network. Ad networks save advertisers time because they have already established relationships with a multitude of online publishers. Publishers, ad networks and advertisers share in the profit generated by specific ads.
Vertical networks allow for the most control with regard to advertisers knowing when and where their ads will show. These types of networks also tend to cost the most. Blind networks are cheaper, but offer much less control for the advertiser. Advertisers often do not know specifically when and where their ads will show, but are guaranteed frequent showings of their ads on numerous publisher websites. Targeted networks pay attention to specific demographics or geographical areas. Ads are placed with publishers who best represent the characteristics of the advertiser.