product line vs product

product line and product both are nouns.

Word	Noun	Adjective	Verb	Adverb
product line	Yes	No	No	No
product	Yes	No	No	No

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

Other hypernyms of product line include merchandise, ware.

product line (noun)	product (noun)
a particular kind of product or merchandise	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