Based on the networks' prior performance in terms of yield (eCPM), fill rate, latency, and other factors, a ladder of networks is placed from top to bottom in order of performance to the publisher.
Header bidding is an advanced form of programmatic advertising that enables publishers to simultaneously offer their ad inventory to a number of ad networks and exchanges.
Inventory is sold via waterfall to the first advertiser in line, whereas header bidding assures that it is sold to the highest bidder. While waterfall adopts a sequential auction model that increases latency, header bidding occurs in real-time.