apple tree vs fruit tree

apple tree and fruit tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
apple tree	Yes	No	No	No
fruit tree	Yes	No	No	No

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

apple tree: any tree of the genus Malus especially those bearing firm rounded edible fruits
fruit tree: tree bearing edible fruit

apple tree (noun)	fruit tree (noun)
any tree of the genus Malus especially those bearing firm rounded edible fruits	tree bearing edible fruit