That confused me too. Made me a little angry when I was looking for something in Documents. I went to Users\username\Documents and the data wasn't in that folder. Turns out Windows maintained two Documents folders. That one + OneDrive\Documents.

I had uninstalled OneDrive the first time I used this laptop. But that wasn't enough. I had to reinstall OneDrive. Turn off folder backups. Unlink the PC from OneDrive. Then uninstall it again. That fixed the two Documents folders problem. OneDrive\Documents went away and the contents put back into Users\username\Documents.

A fairly frustrating experience and wasted about an hour troubleshooting it.