possibility vs being

possibility and being both are nouns.

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

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

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

possibility (noun)	being (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	a living thing that has (or can develop) the ability to act or function independently
a possible alternative	the state or fact of existing
a future prospect or potential
capability of existing or happening or being true