Meaning of “behind” - Learner’s Dictionary

behind

preposition uk us /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.
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)