A backup is a copy of a website that is kept on a different hosting server and can be restored if a problem occurs with the live Internet site - an unsuccessful script update, an unintentional deletion of a file or of the whole database, etc. Restoring the site the way it was shall eliminate or decrease the damage the issue may have caused, that is by all means an obviously better option than having to rebuild your whole Internet site from scratch. While you may download a copy of your content on your PC, keeping a backup is a function that almost all hosting providers include as part of their plans. You must check how often they do that, though, because some service providers generate a backup only once every 7 days, which can be far from enough for a booking website or an e-commerce portal where the data is updated daily. It's adviseable to see how easily a backup can be restored, which can be critical if some issue appears on your site.