caldera vs volcanic crater

caldera and volcanic crater both are nouns.

Word	Noun	Adjective	Verb	Adverb
caldera	Yes	No	No	No
volcanic crater	Yes	No	No	No

As nouns, volcanic crater is a hypernym of caldera; that is, volcanic crater is a word with a broader meaning than caldera:

caldera: a large crater caused by the violent explosion of a volcano that collapses into a depression
volcanic crater: a bowl-shaped geological formation at the top of a volcano

Other hypernyms of caldera include crater.

caldera (noun)	volcanic crater (noun)
a large crater caused by the violent explosion of a volcano that collapses into a depression	a bowl-shaped geological formation at the top of a volcano