A backup is an insurance copy of your website. Good backups run automatically, usually daily, and are stored somewhere other than the server the site runs on, so one failure does not take out both.
What matters is whether the backup can actually be restored, how far back the copies go, and who knows how to do it. A backup nobody has ever tested is a hope rather than a plan.
If your site takes bookings or orders, the database with those records needs backing up too, not just the pages.
Without a backup, a hack, a failed update or a hosting company going bust can mean paying for a whole new website. With one, it is often a quick restore. Ask your web provider directly: how often, stored where, and how quickly can you restore it.