Transaction-level advisory lock unlocking and transaction end

Hi,

I could not understand on the basis of documentation about transaction-level
advisory lock:

> Transaction-level lock requests ... are automatically released at the end
of the transaction ...

So, what order will the use of transactions and unlock the lock?
The transaction would be applied at first and the lock would be unlocked
after it or vice versa?
Or any order in this case is not guaranteed?

Thanks a lot for your help.

Saimon