Meaning of “behind” - Learner’s Dictionary

behind

preposition us uk /bɪˈhaɪnd/
BACK

A1 at or to the back of someone or something:

Close the door behind you.
The warehouse is behind the store.
The letter had fallen behind the desk.

More examples

LESS SUCCESSFUL

B1 slower or less successful than someone or something:

Our team is 3 points behind the winners.
The building work is already behind schedule (= late).
CAUSING

causing something, or responsible for something:

What was the reason behind her decision to leave?
SUPPORTING

B1 giving your help or support to someone:

The group is 100 percent behind her.
NOT AFFECTING

If a bad experience or your own bad behaviour is behind you, it does not exist or affect your life now:

He's put his criminal past behind him.

(Definition of “behind preposition” from the Cambridge Learner’s Dictionary © Cambridge University Press)