It also restored the dislike button and added support for sponsorblock (which can automatically skip sponsor segments, as well as intros, outros, "like and subscribe" reminders, non-music sections of music videos, and other fluff.)
The name comes from it being an "advanced" YouTube app, only without any "ad"s ;)
Oh, and you could disable the comments section!
All-in-all, it just made YouTube a much better experience.