An Ad Exchange is a digital marketplace where advertisers and publishers buy and sell ad inventory via real-time bidding (RTB). Ad exchanges connect demand-side platforms (DSPs) and supply-side platforms (SSPs), facilitating transactions for ad space on websites and apps.

This model offers transparency, efficiency, and flexibility, allowing advertisers to access vast ad inventory at competitive prices. For publishers, ad exchanges increase demand for their ad space, potentially driving up revenue through competitive bidding.