We decided to include Akeeba Backup in our Glossary of Joomla Terms purely based on how vital it is for any Joomla based website. Especially for beginners.
Akeeba Backup actually is not a part of your Joomla Content Management System. It is a third party extension. You need to download it from the download section at AkeebaBackup.com website and install it on your Joomla site.
Once you installed it, you can use it to create your website backups with one click or automatically, by a certain schedule.
In case something happened to your site, you can easily restore it with the backup you created with the Akeeba Backup component.