snapper vs red snapper

snapper and red snapper both are nouns.

Word	Noun	Adjective	Verb	Adverb
snapper	Yes	No	No	No
red snapper	Yes	No	No	No

As nouns, red snapper is a hyponym of snapper; that is, red snapper is a word with a more specific, narrower meaning than snapper:

snapper: any of several large sharp-toothed marine food and sport fishes of the family Lutjanidae of mainly tropical coastal waters
red snapper: an esteemed food fish with pinkish red head and body; common in the Atlantic coastal waters of North America and the Gulf of Mexico

As nouns, red snapper is a hyponym of snapper; that is, red snapper is a word with a more specific, narrower meaning than snapper:

snapper: flesh of any of various important food fishes of warm seas
red snapper: highly esteemed reddish lean flesh of snapper from Atlantic coast and Gulf of Mexico

snapper (noun)	red snapper (noun)
large-headed turtle with powerful hooked jaws found in or near water; prone to bite	an esteemed food fish with pinkish red head and body; common in the Atlantic coastal waters of North America and the Gulf of Mexico
any of several large sharp-toothed marine food and sport fishes of the family Lutjanidae of mainly tropical coastal waters	highly esteemed reddish lean flesh of snapper from Atlantic coast and Gulf of Mexico
Australian food fish having a pinkish body with blue spots
a party favor consisting of a paper roll (usually containing candy or a small favor) that pops when pulled at both ends
flesh of any of various important food fishes of warm seas
(football) the person who plays center on the line of scrimmage and snaps the ball to the quarterback