What does this mean?

Self absorbed… not aware of people around them or what’s going on… stuck in thought…

{@saltlife97] in a world of your own basically means you are not concentrating on the matter in hand and thinking about other things that have no relevance

That they prefer the world in their head more than the real one, probably depressed or just an air head.

Lost in their mind

Definition of in one's own world
: spending so much time thinking about something that one does not notice what is happening I tried to talk to him, but he was in his own (little) world and didn't seem to hear what I was saying