So I’m not the best at this, but this is my best guess (I have no experience in sysadmin, as I’ve only ever been the sole user of my PC and prefer not to network anything).

Owner #1, smackyboi, has ownership of a file called smutgame.AppImage. This means they can choose who accesses smutgame, if it can execute, if it can be read or written by certain groups, etc.

Owner #2, luvurealgood, on the system via their own account (or networked computer in the case of server storage) can’t change these settings unless smackyboi says they could, because they’re the owner and can add luvurealgood to the admin group for the file if they want. Smackyboi suddenly writes, sudo chown luvurealgood smutgame.AppImage.

Now luvurealgood owns that file and can make every change they want to it, including removing smackyboi from accessing it, as they’re no longer the owner. They can lock down the file and forbid it from being executed, etc etc. I believe anyone who is in the admin group of that file can do anything to it as well, except change it’s ownership if its already owned.

This is just from pieces of info and my tiny experience in Windows sysadmin shenanigans. Someone swoop in and correct me if I got anything wrong.