collector's item vs curiosity

collector's item and curiosity both are nouns.

Word	Noun	Adjective	Verb	Adverb
collector's item	Yes	No	No	No
curiosity	Yes	No	No	No

As nouns, curiosity is a hypernym of collector's item; that is, curiosity is a word with a broader meaning than collector's item:

collector's item: the outstanding item (the prize piece or main exhibit) in a collection
curiosity: something unusual -- perhaps worthy of collecting

Other hypernyms of collector's item include curio, oddity, oddment, peculiarity, rarity.

collector's item (noun)	curiosity (noun)
the outstanding item (the prize piece or main exhibit) in a collection	something unusual -- perhaps worthy of collecting
	a state in which you want to learn more about something