goose vs greylag goose

goose and greylag goose both are nouns.

Word	Noun	Adjective	Verb	Adverb
goose	Yes	No	Yes	No
greylag goose	Yes	No	No	No

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

goose: web-footed long-necked typically gregarious migratory aquatic birds usually larger and less aquatic than ducks
greylag goose: common grey wild goose of Europe; ancestor of many domestic breeds

goose (noun)	greylag goose (noun)
web-footed long-necked typically gregarious migratory aquatic birds usually larger and less aquatic than ducks	common grey wild goose of Europe; ancestor of many domestic breeds
flesh of a goose (domestic or wild)
a man who is a stupid incompetent fool