Real-time bidding (RTB) is a type of media buying within the field of programmatic advertising. RTB refers to the process in which ads are bought and sold in a real-time auction that takes place during the time for a web page or app to load. Real-time bidding is just one piece of the programmatic advertising ecosystem and often relies on a supply-side platform (SSP) or ad exchange and demand-side platforms (DSPs) to facilitate near-instant auctions between ad buyers and sellers of ad inventory.