When you backup your website you create copies of both the files and the database.
General backup best practices
Backup your Drupal files
Migrating Drupal site if you change hosts, or if you maintain separate development and live sites.
Here's a perl script that should properly backup a multisite Drupal installation. I've tested it on my site and it seems to work, but it
Most site updates happen without incident and when successful, the database dump you made can be discarded or archived. However,