top side vs desktop

top side and desktop both are nouns.

Word	Noun	Adjective	Verb	Adverb
top side	Yes	No	No	No
desktop	Yes	No	No	No

As nouns, desktop is a hyponym of top side; that is, desktop is a word with a more specific, narrower meaning than top side:

Other hyponyms of top side include crest, crown, poll, crown, pate, poll, rooftop, tiptop.

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