shooter vs sharpshooter

shooter and sharpshooter both are nouns.

Word	Noun	Adjective	Verb	Adverb
shooter	Yes	No	No	No
sharpshooter	Yes	No	No	No

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

shooter: a person who shoots (usually with respect to their ability to shoot)
sharpshooter: someone skilled in shooting

Other hyponyms of shooter include crack shot, marksman, gun, gunman, trapshooter.

shooter (noun)	sharpshooter (noun)
a large marble used for shooting in the game of marbles	a fast schooner once used by New England fisherman for illegal fishing in Canadian waters
a person who shoots (usually with respect to their ability to shoot)	someone skilled in shooting
a professional killer who uses a gun	an athlete noted for accurate aim
(sports) a player who drives or kicks a ball at the goal (or a basketball player who shoots at the basket)
a gambler who throws dice in the game of craps