Disks and data
Backups
Copies of a server or data you can restore from after a mistake or a hack.
A backup is a copy of data on another disk or in another place. It saves you when something goes wrong: an update broke the site, the wrong file got deleted, the server was hacked.
Some providers make backups for free — daily or weekly — others sell them separately. Where the copy is stored matters: on the same server it protects little. For your own data, set up your own backups elsewhere too.