You can backup your Joomla system running on a hosted server by using a powerful component which is the Akeeba Backup. Installing this component enables you create a backup files of the entire database of your joomla site. You can even download and save it in your secured storage device.
It is easy to backup your Joomla site using this component, however, in restoring your joomla driven website, it is a bit complicated. You need to use the Akeeba Kickstart, you can see the full instructions in their website.