What is RAID, and is it a backup? Do I need it with one drive?

I keep seeing people say RAID in homelab videos and comments, and some talk like it's a backup and others say it's definitely not. I'm confused about which one is right. My plan is a single mini PC with one drive in it, so I don't even know if RAID applies to me.

From what I can tell, it's using more than one drive together so you don't lose stuff if one dies. But if that's true, why do people say it's not a backup? Would I need a second drive just to try it, or is it something I can skip at the start and just copy my files somewhere else? What would you do if you only had one drive?

I agree that RAID is not a backup, its a safety net for if you have hardware failures.

I think the main difference that isn't always explained well is that RAID is like an instant copy across X amount of drives, so if you corrupt the files they instantly get corrupted on the other drives. Where as a backup is a snapshot in a point of time.

Kind of an old video but it does show some components of a RAID.

Play video Loads from YouTube when you play it