An ad network, or advertising network, is a company that connects advertisers with websites or other platforms that are willing to host their ads. Ad networks typically work by aggregating inventory from a large number of publishers, and then selling that inventory to advertisers, either directly or through an auction or bidding process. Ad networks can provide advertisers with access to a large and diverse audience, and can help publishers monetize their content by filling their ad inventory with relevant and high-paying ads. Ad networks often provide additional services, such as ad serving, tracking, and reporting, to help advertisers and publishers manage and optimize their campaigns and revenues. Ad networks can operate on a variety of business models, including cost-per-click (CPC), cost-per-impression (CPM), and cost-per-action (CPA).