concert vs rock concert

concert and rock concert both are nouns.

Word	Noun	Adjective	Verb	Adverb
concert	Yes	No	Yes	No
rock concert	Yes	No	No	No

As nouns, rock concert is a hyponym of concert; that is, rock concert is a word with a more specific, narrower meaning than concert:

concert: a performance of music by players or singers not involving theatrical staging
rock concert: a performance of rock music

concert (noun)	rock concert (noun)
a performance of music by players or singers not involving theatrical staging	a performance of rock music

concert (verb)	rock concert (verb)
settle by agreement
contrive (a plan) by mutual agreement