bubbler vs fountain

bubbler and fountain both are nouns.

Word	Noun	Adjective	Verb	Adverb
bubbler	Yes	No	No	No
fountain	Yes	No	No	No

As nouns, fountain is a hypernym of bubbler; that is, fountain is a word with a broader meaning than bubbler:

bubbler: a public fountain to provide a jet of drinking water
fountain: a structure from which an artificially produced jet of water arises

bubbler (noun)	fountain (noun)
a public fountain to provide a jet of drinking water	a plumbing fixture that provides a flow of water
any of various devices in which air or some other gas is bubbled through a liquid	an artificially produced flow of water
	a structure from which an artificially produced jet of water arises
	a natural flow of ground water