push button vs buzzer

push button and buzzer both are nouns.

Word	Noun	Adjective	Verb	Adverb
push button	Yes	No	No	No
buzzer	Yes	No	No	No

As nouns, buzzer is a hyponym of push button; that is, buzzer is a word with a more specific, narrower meaning than push button:

push button: an electrical switch operated by pressing
buzzer: a push button at an outer door that gives a ringing or buzzing signal when pushed

Other hyponyms of push button include bell push, bell, doorbell, horn button, mouse button, panic button, reset button.

push button (noun)	buzzer (noun)
an electrical switch operated by pressing	a push button at an outer door that gives a ringing or buzzing signal when pushed
	a signaling device that makes a buzzing sound