popularity vs hot stuff

popularity and hot stuff both are nouns.

Word	Noun	Adjective	Verb	Adverb
popularity	Yes	No	No	No
hot stuff	Yes	No	No	No

As nouns, hot stuff is a hyponym of popularity; that is, hot stuff is a word with a more specific, narrower meaning than popularity:

popularity (noun)	hot stuff (noun)
the quality of being widely admired or accepted or sought after	the quality of being attractive and exciting (especially sexually exciting)
	the quality of being popular