Percona's Xtrabackup backup all files or only the database?

Hello

I am testing Percona's xtrabackup tool on a test server with only one (MariaDB) database inside named "database1" and i got the backup using:

innobackupex /path/to/backupdir/

Code (markup):

Then i go to the path to check the files inside and i notice that all files from /var/lib/mysql/ are there ....

This is the way it should work?

I thought that it will copy only the database and not all the rest of the files....

If this is the way that it works and i move to another server after setting up a newest mysql version and import all those files it will work?

What about passwords as in the new mysql server i will use different passwords.....

If should not work like this how can i set it to backup only my database and not the rest (if the rest is not needed it) ?

Thank you