concrete poem vs poem

concrete poem and poem both are nouns.

Word	Noun	Adjective	Verb	Adverb
concrete poem	Yes	No	No	No
poem	Yes	No	No	No

As nouns, poem is a hypernym of concrete poem; that is, poem is a word with a broader meaning than concrete poem:

concrete poem: a poem whose meaning is conveyed through its graphic shape or pattern on the printed page.
poem: a composition written in metrical feet forming rhythmical lines

Other hypernyms of concrete poem include verse form.

concrete poem (noun)	poem (noun)
a poem whose meaning is conveyed through its graphic shape or pattern on the printed page.	a composition written in metrical feet forming rhythmical lines