Why does Adaway want to install a self signed certificate?

One of the best trends these days is the shift to encrypted Internet traffic, aka Transport Layer Security or TLS, and mobile apps are not the exception, often when testing a mobile app we need/want to see the data being sent from and received on our mobile devices but since most of the apps are using TLS on their network requests we cannot just proxy the traffic and understand the communication between the app and its server.

Adaway uses it to block ads efficiently (which is kinda obvious from the paragraph above :) )