Keeping regular backups is important, in case your web host dies or you get hacked or you accidentally delete a bunch of data. Ideally you should be downloading regular backups of your entire hosting account from your web hosting control panel, such as cpanel... but if not, WSN can help you with backups.
Go to Admin Panel -> Maintenance -> Backups to manage your backups. These are sql database backups, not file backups. If your site doesn't function after rolling back to a database from a day when it did function, that means the database wasn't the problem and you need to overwrite the files instead (download the .tar.gz from the customer downloads area and perform a manual upgrade).
If you can't reach the admin panel due to a database error, check the "backups" subdirectory on your site. You can restore a WSN-generated backup via phpmyadmin or via SSH terminal.
The automated backups system saves the number of days of backups which you request in order to give you a variety of restore point options. If you set it to save 0, you'll be able to do manual backups but no automatic backups will be generated.
Note: if you're trying to duplicate your site in a second location, use Admin Panel -> Miscellaneous -> Clone Utility instead of the backup utility.
Important note: Generating a backup isn't very useful if you don't download it. If you have hosting problems or get hacked, all files on the server could be deleted. Be sure to regularly copy backup files to your computer or a cloud storage service.
Although WSN doesn't have a file backup mechanism per-se, the theme packager can be used as one since it can generate a package containing most or all of your customizations. Go to Admin Panel -> Themes -> Theme Packager to generate a package, and Admin Panel -> Themes -> Add Themes to restore one.