possibility vs existence

possibility and existence both are nouns.

Word	Noun	Adjective	Verb	Adverb
possibility	Yes	No	No	No
existence	Yes	No	No	No

As nouns, existence is a hypernym of possibility; that is, existence is a word with a broader meaning than possibility:

Other hypernyms of possibility include being, beingness, face of the earth.

possibility (noun)	existence (noun)
a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena	everything that exists anywhere
a possible alternative	the state or fact of existing
a future prospect or potential
capability of existing or happening or being true