piece goods vs product

piece goods and product both are nouns.

Word	Noun	Adjective	Verb	Adverb
piece goods	Yes	No	No	No
product	Yes	No	No	No

As nouns, product is a hypernym of piece goods; that is, product is a word with a broader meaning than piece goods:

Other hypernyms of piece goods include merchandise, ware.

piece goods (noun)	product (noun)
merchandise in the form of fabrics sold by the yard	an artifact that has been created by someone or some process
	items for sale to the individual consumer
	a quantity obtained by multiplication
	the set of elements common to two or more sets
	a consequence of someone's efforts or of a particular set of circumstances
	a chemical substance formed as a result of a chemical reaction