RTB bid request, also known as real-time bidding bid request, is a digital advertising term that refers to the process of buying and selling online ad space in real-time through an auction-based system. This system allows advertisers to bid on ad space in milliseconds, targeting specific audiences and maximizing the value of each impression. On the other hand, SSP, or supply-side platform, is a technology used by publishers to manage and sell their ad inventory to multiple ad exchanges and demand-side platforms. It acts as a middleman between publishers and advertisers, optimizing the sale of ad space and maximizing revenue for publishers. Together, RTB bid request and SSP enable the efficient and effective buying and selling of online advertising, making it a crucial component of the digital advertising ecosystem.