snail vs garden snail

snail and garden snail both are nouns.

Word	Noun	Adjective	Verb	Adverb
snail	Yes	No	Yes	No
garden snail	Yes	No	No	No

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

snail: freshwater or marine or terrestrial gastropod mollusk usually having an external enclosing spiral shell
garden snail: any of several inedible snails of the genus Helix; often destructive pests

Other hyponyms of snail include scorpion shell, edible snail, Helix pomatia.

snail (noun)	garden snail (noun)
freshwater or marine or terrestrial gastropod mollusk usually having an external enclosing spiral shell	any of several inedible snails of the genus Helix; often destructive pests
edible terrestrial snail usually served in the shell with a sauce of melted butter and garlic

snail (verb)	garden snail (verb)
gather snails