gathering vs social group

gathering and social group both are nouns.

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

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

gathering (noun)	social group (noun)
the social act of assembling	people sharing some social relation
the act of gathering something
sewing consisting of small folds or puckers made by pulling tight a thread in a line of stitching
a group of persons together in one place