desktop vs upside

desktop and upside both are nouns.

Word	Noun	Adjective	Verb	Adverb
desktop	Yes	No	No	No
upside	Yes	No	No	No

As nouns, upside is a hypernym of desktop; that is, upside is a word with a broader meaning than desktop:

Other hypernyms of desktop include top, top side, upper side.

desktop (noun)	upside (noun)
(computer science) the area of the screen in graphical user interfaces against which icons and windows appear	the highest or uppermost side of anything
the top of a desk