A backup is a copy of a site that is kept on a separate server and could be restored if something wrong happens with the live website - an unsuccessful script update, an unintended deletion of some file or of the entire database, etc. Restoring the site the way it was shall remove or minimize the damage the issue may have caused, that's by all means an obviously better option than having to reconstruct the whole site from scratch. While you may download a copy of your content on your laptop, keeping a backup is a function that most website hosting providers include as part of their packages. You'll have to take a look at how frequently they do that, though, because some providers generate a backup only once every couple of days, which can be far from enough for a booking site or an e-commerce portal in which the data is updated daily. It's adviseable to see how fast and easy a backup could be restored, which could be vital if some issue appears on your Internet site.