What does "AdX" mean?

AdX:

AdX is Google's Advertising Exchange used to be called DoubleClick Ad Exchange. It is an advertising network for bigger players (to sign up one needs 5 Million visitors per month to one's website) providing an interface that offers real-time bidding (RTB) for places to put one's advertising, in such advertising networks as AdSense and those provided by other advertising agencies and demand-side platforms [DSP's]. AdX is essentially a "walled garden", providing what looks like an unfair advantage to its users, while excluding smaller players.

 Ad Push Up: AdX vs. AdSense

 BlockThrough: AdX