A backup is a copy of a site that is kept on a separate hosting server and can be restored if a problem occurs with the live website - a defeated script update, an accidental deletion of a file or of the whole database, and so forth. Restoring the site the way it was will take away or lessen the damage the issue may have caused, that's by all means an obviously better alternative than having to reconstruct the entire site from scratch. Although you can download a copy of your content on your personal computer, keeping a backup is a functionality that most web hosting companies include as part of their packages. It is important to check how often they do that, though, because some companies create a backup just once every couple of days, that could be far from enough for a booking Internet site or an e-commerce portal in which the information is updated every day. It's also advisable to see how fast and easy a backup could be restored, which could be critical if some problem appears on your website.