willow tree vs Salix

willow tree and Salix both are nouns.

Word	Noun	Adjective	Verb	Adverb
willow tree	Yes	No	No	No
Salix	Yes	No	No	No

willow tree (noun)	Salix (noun)
any of numerous deciduous trees and shrubs of the genus Salix	a large and widespread genus varying in size from small shrubs to large trees: willows