comforter vs duvet

comforter and duvet both are nouns.

Word	Noun	Adjective	Verb	Adverb
comforter	Yes	No	No	No
duvet	Yes	No	No	No

As nouns, duvet is a hyponym of comforter; that is, duvet is a word with a more specific, narrower meaning than comforter:

comforter: bedding made of two layers of cloth filled with stuffing and stitched together
duvet: a soft quilt usually filled with the down of the eider

Other hyponyms of comforter include continental quilt, eiderdown, patchwork, patchwork quilt.

comforter (noun)	duvet (noun)
bedding made of two layers of cloth filled with stuffing and stitched together	a soft quilt usually filled with the down of the eider
device used for an infant to suck or bite on
a person who commiserates with someone who has had misfortune
a person who reduces the intensity (e.g., of fears) and calms and pacifies