An Ad Network is a platform that connects advertisers with publishers looking to sell ad space. It aggregates ad inventory from multiple publishers, creating a marketplace where advertisers can bid for placements to reach specific audiences. Examples include Google Display Network and Media.net.

Ad networks simplify the ad-buying process, providing access to a large audience pool. For publishers, ad networks fill inventory, generate revenue, and increase exposure. This setup benefits both advertisers and publishers by offering a streamlined way to manage ad placements.