How to Back Up and Restore Windows 11 Files and Settings?

Oh my, thank you both for such detailed answers! I’m a bit overwhelmed with all the technical terms though, if I’m being honest.

I mainly want to make sure my grandchildren’s photos and school projects are safe when they visit and use my computer. Would OneDrive be the simplest option for someone like me who isn’t very tech-savvy? And does backing up protect against those nasty viruses I keep hearing about on the news? I worry about the kids accidentally clicking on something bad.

Also, if I use OneDrive, do I need to buy something extra, or is it already on my Windows 11 computer? I just want to keep things simple and safe for the little ones.