Real-Time Bidding (RTB) is the process of buying and selling ads in real-time on a per-impression basis. In the RTB process, a DSP, an ad exchange, and an SSP are involved. Through the RTB process, the advertiser can bid on specific inventory that they would like to purchase from a specific publisher. This is done in an instantaneous manner.
The pricing is done on a CPM (Cost per Mille) basis. There is an auction process put in place where the highest bidder gets access to the ad inventory. The winning bidder’s ads are instantly loaded onto the publishers’ site. This whole process lets a few milliseconds finish up.
It is important to remember that RTB is a type of programmatic advertising. Not all programmatic advertising uses RTC. Some programmatic advertising technology sells publisher inventory at a fixed price instead of an open-auction concept.