An ad network is a digital hub that acts as an intermediary between advertisers and publishers of websites or apps. Its main function is to facilitate the process of buying and selling advertising space. Ad networks collect ad slots from different publishers and make them available for advertisers to buy.

Through an ad network, advertisers can reach a wider audience by buying ad space in several different places at the same time. Publishers, on the other hand, can benefit from ad networks by filling their empty ad slots with relevant ads and generating revenue.

Ad networks often also offer different types of targeting and reporting options to help advertisers reach their desired audience and measure results.