coconut palm vs palm tree

coconut palm and palm tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
coconut palm	Yes	No	No	No
palm tree	Yes	No	No	No

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

coconut palm: tall palm tree bearing coconuts as fruits; widely planted throughout the tropics
palm tree: any plant of the family Palmae having an unbranched trunk crowned by large pinnate or palmate leaves

Other hypernyms of coconut palm include palm.

coconut palm (noun)	palm tree (noun)
tall palm tree bearing coconuts as fruits; widely planted throughout the tropics	any plant of the family Palmae having an unbranched trunk crowned by large pinnate or palmate leaves