Real-time bidding (RTB) is a means by which advertising inventory is bought and sold on a per-impression basis, via programmatic instantaneous auction, similar to financial markets. With real-time bidding, advertising buyers bid on an impression and, if the bid is won, the buyer’s ad is instantly displayed on the publisher’s site. Real-time bidding lets advertisers manage and optimize ads from multiple ad-networks by granting the user access to a multitude of different networks, allowing them to create and launch advertising campaigns, prioritize networks and allocate percentages of unsold inventory, known as backfill.
Real-time bidding is distinguishable from static auctions by how it is a per-impression way of bidding whereas static auctions are groups of up to several thousand impressions. Overall, when compared to static auctions, RTB is more effective for both advertisers and publishers in terms of advertising inventory sold.