Here's how a typical banner/adspace currently works: 1. The ad/banner space downloads a javascript file 2. Javascript runs, collects browser+cookie+other identifying information and sends it on up to an ad exchange 3. The ad-exchange systems cross-reference the information it receives with other information it already has (think huge low latency k/v store) in order to try to identify you further, perform cross-device…
It's called a Vickrey Auction. It allows bidders to bid their true value (instead of trying to outbid all of the other bidders, as is what results from a first-price auction).