An ad network bundles. It signs up hundreds or thousands of websites and apps, pools their ad space, and sells that inventory to advertisers as a single buy. The publisher gets filled slots without hiring a sales team. The advertiser gets reach without negotiating site by site.

Networks typically take a cut of the revenue, often somewhere between fifteen and thirty percent, though the range varies widely. Some specialize by vertical, like gaming or finance. Others focus on a format, such as mobile video or native placements.

What networks handle

• Aggregating publisher inventory
• Targeting and delivery technology
• Reporting and billing
• Payment collection from advertisers

Exchanges and networks get confused constantly. A network buys and resells inventory. An exchange provides the auction venue. Many companies run both under one roof.