butter cookie vs biscuit

butter cookie and biscuit both are nouns.

Word	Noun	Adjective	Verb	Adverb
butter cookie	Yes	No	No	No
biscuit	Yes	No	No	No

As nouns, biscuit is a hypernym of butter cookie; that is, biscuit is a word with a broader meaning than butter cookie:

Other hypernyms of butter cookie include cookie, cooky.

butter cookie (noun)	biscuit (noun)
cookie containing much butter	small round bread leavened with baking-powder or soda
	any of various small flat sweet cakes