punk rock vs rock'n'roll

punk rock and rock'n'roll both are nouns.

Word	Noun	Adjective	Verb	Adverb
punk rock	Yes	No	No	No
rock'n'roll	Yes	No	No	No

As nouns, rock'n'roll is a hypernym of punk rock; that is, rock'n'roll is a word with a broader meaning than punk rock:

punk rock: rock music with deliberately offensive lyrics expressing anger and social alienation; in part a reaction against progressive rock
rock'n'roll: a genre of popular music originating in the 1950s; a blend of black rhythm-and-blues with white country-and-western

Other hypernyms of punk rock include rock-and-roll, rock 'n' roll, rock, rock and roll, rock music.

punk rock (noun)	rock'n'roll (noun)
rock music with deliberately offensive lyrics expressing anger and social alienation; in part a reaction against progressive rock	a genre of popular music originating in the 1950s; a blend of black rhythm-and-blues with white country-and-western