porc vs cochon de lait

porc and cochon de lait both are nouns.

Word	Noun	Adjective	Verb	Adverb
porc	Yes	No	No	No
cochon de lait	Yes	No	No	No

As nouns, cochon de lait is a hyponym of porc; that is, cochon de lait is a word with a more specific, narrower meaning than porc:

Other hyponyms of porc include suckling pig, salt pork, pigs' feet, pigs' knuckles.

porc (noun)	cochon de lait (noun)
meat from a domestic hog or pig	whole young pig suitable for roasting