The image explains most of it. The ‘My Stuff’ category is confusing when ‘My Library’ already exists.
Looking at the My Library section, I don’t know why Tracks, Composers and Compilations are a permanent part of the menu either. Granted I know you’re not a real Audiophile if you don’t have a Classical collection so hence Composers but I can’t see someone with hundreds+ albums wanting to see a list of all the tracks in their library.
Years later I still can’t find a use for Tags.