Header bidding allows publishers to simultaneously auction their ad inventory to multiple demand sources, including ad exchanges and SSPs, enabling them to maximize their revenue by securing the highest possible bids for their available ad space. In contrast, real-time bidding (RTB) involves automated, real-time auctions for ad impressions but may not consider all demand sources simultaneously. This can result in potentially lower yields for publishers as compared to the more comprehensive and revenue-optimized approach of header bidding.