What do UI sounds include?

I know it controls the volume of pm notifications, but is that it? i'm not sure what other noises the user interface could possibly incorporate audio-wise.

I'm led to believe it controls the volume of other noises as well with a such a broad description, if not i figure it'd just say PM notification volume or something.

curiosity, that's all.

it also controls the warnings, like, "Invalid Spell Target", "That skill is still Recharging" etc etc.

PM notification, people lvling up, skill cancelations