The AdEx Network has several layers: the first one is the ad exchange, which is built on Ethereum smart contracts with a few solutions for a quicker layer on top of that (or side-by-side) being experimented upon. The ad exchange is built in a way to facilitate the entire relationship between publishers, advertisers and end users, therefore replacing the usual network of multiple exchanges, SSPs and DSPs and all the complexity, inaccurancy and inefficiency that comes with it.
On top of the exchange, we are building dapps for the publisher portal, advertiser portal and the AdEx profile (for end users). Dapps are distributed applications that connect to the Ethereum blockchain and interact with it, but typically with a user-friendly user interface. All of those dapps will be browser-based and easily accessible online, hosted by AdEx - but since they're interacting with the blockchain directly, anyone can run their own instance of those dapps if they want to.