Quercus ilex vs oak tree

Quercus ilex and oak tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Quercus ilex	Yes	No	No	No
oak tree	Yes	No	No	No

As nouns, oak tree is a hypernym of Quercus ilex; that is, oak tree is a word with a broader meaning than Quercus ilex:

Quercus ilex: evergreen oak of southern Europe having leaves somewhat resembling those of holly; yields a hard wood
oak tree: a deciduous tree of the genus Quercus; has acorns and lobed leaves

Other hypernyms of Quercus ilex include oak.

Quercus ilex (noun)	oak tree (noun)
evergreen oak of southern Europe having leaves somewhat resembling those of holly; yields a hard wood	a deciduous tree of the genus Quercus; has acorns and lobed leaves