ensemble vs pop group

ensemble and pop group both are nouns.

Word	Noun	Adjective	Verb	Adverb
ensemble	Yes	No	No	No
pop group	Yes	No	No	No

As nouns, pop group is a hyponym of ensemble; that is, pop group is a word with a more specific, narrower meaning than ensemble:

Other hyponyms of ensemble include gamelan, jug band, mariachi, skiffle group.

ensemble (noun)	pop group (noun)
a coordinated outfit (set of clothing)	a group that plays pop music
the chorus of a ballet company
a group of musicians playing or singing together
an assemblage of parts or details (as in a work of art) considered as forming a whole
a cast other than the principals