I tried to bind a key using a prefix-key of C-z, but Emacs told me: Key sequence C-z c starts with non-prefix key C-z. I guess this means that C-z is already bound to something.
So I tried to do M-x describe-key RET C-z, but when I do that it doesn't describe that key, it just waits for the next key press (by adding a hyphen after C-z).
How can I tell describe-key that I just want to know what C-z is?