A backup of an Internet site is a copy of its content, that is kept on a different server and could be restored if something happens. This feature is quite effective, because you cannot know if a script update shall not go wrong or if you will not delete something unintentionally - a file, a folder, a database entry, etc. When your Internet site is backed up, it can be restored the way it was before the issue appeared, so there won't be any damage, or at least it'll be small, depending upon the specific scenario. Keeping backups on your computer is not very feasible, due to the fact that you would need to do it at least once each day and you may still lose info if your last backup isn't recent enough. In this light, you will have to rely on your website hosting company, so you have to double-check their policy on the backups, because some companies create backups just once per week, which will do no good if a problem occurs with an Internet site that is being used and updated constantly, like an online store, for instance.
