Your site uses an online database to keep track of all the content and many of the settings in your Joomla website. It's best to have a backup system in place incase something goes wrong!

Webhost Backups
Most webhosts will backup your website daily although its not always easy to retrieve a backup when you want it.

Joomla Backups
The content of your website is in an SQL database.

For our customers we have an auto backup system that makes a daily backup copy of this database file, usually between midnight and 6am. If something goes terribly wrong you can restore your site using the last backup available.

Manual Backups
You can also manually backup the database before working on the site using one of the backup components available for Joomla in the Backup section of the Joomla Extensions Directory.