What is the AdEx protocol?

Could you please explain to me in detail what exactly the AdEx protocol is? I understand it's somehow related to the world of cryptocurrency and finance, but I'm curious to know how it specifically functions and what benefits it offers to its users. Is it a decentralized platform for advertising? And if so, how does it ensure transparency and security for both advertisers and users? Additionally, what sets it apart from other similar platforms in the market? I'd appreciate a clear and concise explanation of its core features and how it operates.