The ad ecosystem is complex. Here’s what happens: Advertisers place their ads on demand-side platforms (DSPs), such as Bing, Google, and Yahoo, who then sell the ads to publishers represented by supply-side platforms (SSPs). DSPs and SSPs buy and sell though ad exchanges, who broker these transactions using real-time bidding.

Buying and selling happens within the microseconds it takes for a webpage to load. The targeting data that is exchanged between DSPs and SSPs determines who sees your ad. In other words, you give your ad to a DSP and they sell it to an SSP that represents a publisher, using ad exchanges as the broker.