Bullshit useless notes taken page by page in a boring novel of the teachers choice that if you don't do then you will ask friends for it so you don't fail.
You - "Hey, did you do those annotations last night?"
The endless and time consuming notes most students are required to take when they cannot write in textbooks, usually results in a notebooks filled with sticky notes that are stolen from friends or faked to look like the real notes that should have been taken.
Annoying remarks (annotations) visible by default on internet videos, added by the channel's editor, most of the cases nonsense and/or non-relevant text, blocking large part of the actual picture.
In programming sense... it is kinda small attribute that you tag alongwith some definition... (may be for a method or some attribute). This directly doesn't affect how the programme works, but acts as set of specifications in case someone(some framework or something... is trying to act according to it...