fundraiser vs social gathering

fundraiser and social gathering both are nouns.

Word	Noun	Adjective	Verb	Adverb
fundraiser	Yes	No	No	No
social gathering	Yes	No	No	No

As nouns, social gathering is a hypernym of fundraiser; that is, social gathering is a word with a broader meaning than fundraiser:

fundraiser: a social function that is held for the purpose of raising money
social gathering: a formal or official social gathering or ceremony of people

Other hypernyms of fundraiser include affair, function, occasion, social affair, social function, social occasion.

fundraiser (noun)	social gathering (noun)
a social function that is held for the purpose of raising money	a formal or official social gathering or ceremony of people
someone who solicits financial contributions