fondu vs cheese fondue

fondu and cheese fondue both are nouns.

Word	Noun	Adjective	Verb	Adverb
fondu	Yes	No	No	No
cheese fondue	Yes	No	No	No

As nouns, cheese fondue is a hyponym of fondu; that is, cheese fondue is a word with a more specific, narrower meaning than fondu:

fondu: hot cheese or chocolate melted to the consistency of a sauce into which bread or fruits are dipped
cheese fondue: fondue made of cheese melted in wine for dipping bread and sometimes fruits

Other hyponyms of fondu include chocolate fondue.

fondu (noun)	cheese fondue (noun)
hot cheese or chocolate melted to the consistency of a sauce into which bread or fruits are dipped	fondue made of cheese melted in wine for dipping bread and sometimes fruits
cubes of meat or seafood cooked in hot oil and then dipped in any of various sauces