Thanks for the comment,
yes, desktop is the "computer just on at idle" (where the icons are)
Wall paper is when the computer is on-line, wall paper is used as a backdrop instead of the white BG normally only AOL offers wall papers. That was many years ago, I don't know if AOL offers wall papers any more.
That is just a technical meaning of how both words got there original meaning, but a lot of people just call the desk top, wall paper and vise verse "now a days".
In the above picture, I can't nail down the folders shadow tho.