VACUUM and index

Hello List,

Sorry to send an other e-mail on this subject but it is become a little
bit vague for me.
Imagine you have a database on which a lot of transactions are done
daily : the tables will contain a lot of dead tuples and the B-tree
index too.

If I do a VACUUM on this database, will the B-tree index be scanned,
space reclaimed and made available for re-use ?
Does this action only do by a VACUUM FULL ?
Or is it necessary to do a REINDEX on the index to retrieve a
well-balanced tree ?

Thank you for your help.

Regards,
Alexandra DANTE