filbert vs hazelnut tree

filbert and hazelnut tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
filbert	Yes	No	No	No
hazelnut tree	Yes	No	No	No

As nouns, hazelnut tree is a hypernym of filbert; that is, hazelnut tree is a word with a broader meaning than filbert:

filbert: small nut-bearing tree much grown in Europe
hazelnut tree: any of several shrubs or small trees of the genus Corylus bearing edible nuts enclosed in a leafy husk

Other hypernyms of filbert include hazel, hazelnut.

filbert (noun)	hazelnut tree (noun)
nut of any of several trees of the genus Corylus	any of several shrubs or small trees of the genus Corylus bearing edible nuts enclosed in a leafy husk
small nut-bearing tree much grown in Europe