An ad blocker makes sure your browser never loads ads, trackers and cookie windows. Not hidden — not loaded.
It brings rules with it: lists of addresses that deliver ads and trackers. The browser matches every request against them and drops it before it goes out. That is why a page with a blocker usually finishes sooner, not later.
That depends on the permission it asks for. Anything that inspects every request also sees every page you open. AdSilence does not ask for that permission — so the browser never hands it over.
Three questions: what is switched on out of the box, without you configuring anything? Is there a list of ads that get through for money? And may the extension read your browsing history?