herb tea vs tea

herb tea and tea both are nouns.

Word	Noun	Adjective	Verb	Adverb
herb tea	Yes	No	No	No
tea	Yes	No	No	No

As nouns, tea is a hypernym of herb tea; that is, tea is a word with a broader meaning than herb tea:

herb tea (noun)	tea (noun)
tea-like drink made of leaves of various herbs	a beverage made by steeping tea leaves in water
	a light midafternoon meal of tea and sandwiches or cakes
	dried leaves of the tea shrub; used to make tea
	a tropical evergreen shrub or small tree extensively cultivated in e.g. China and Japan and India; source of tea leaves