water tap vs plumbing fixture

water tap and plumbing fixture both are nouns.

Word	Noun	Adjective	Verb	Adverb
water tap	Yes	No	No	No
plumbing fixture	Yes	No	No	No

As nouns, plumbing fixture is a hypernym of water tap; that is, plumbing fixture is a word with a broader meaning than water tap:

water tap: a faucet for drawing water from a pipe or cask
plumbing fixture: a fixture for the distribution and use of water in a building

Other hypernyms of water tap include faucet, spigot.

water tap (noun)	plumbing fixture (noun)
a faucet for drawing water from a pipe or cask	a fixture for the distribution and use of water in a building