I have a family laptop where I have created separate users for my kids. My user is an admin, theirs are not. I had assumed that having separate users would have separate desktops. But I have installed programs that have their shortcuts showing up on the other users, and then recently one of them changed the desktop background pic, and it changed mine to that as well.
I've learned there is some kind of default or public desktop. I have used Explorer to look at \Users\username\Desktop and the public Desktop, but it still seems odd. I think the public Desktop on the file system did not contain the pictures, files, and program shortcuts that are actually displayed on the everyone's desktop.