[Mashiro]

This will backup the whole vps mysql? 
Root and password will take anything?

This will only backup the database that you specified in the command parameters. If you have several databases you have to run the command for each of the databases to get a backup of them.

The password for the root user that is asked for is the MySQL root user password and not the VPS root password. Instead of using root you should use the username and password for the databases that you used when you set up your applications with the database. In most cases such as when using control panels and similar you don't even get to know to MySQL root password. And newer MySQL/MariaDB servers actually disallow root login for security reason.