tea vs herbal

tea and herbal both are nouns.

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

As nouns, herbal is a hyponym of tea; that is, herbal is a word with a more specific, narrower meaning than tea:

Other hyponyms of tea include cambric tea, cuppa, cupper, herb tea, herbal tea, ice tea, iced tea, sun tea, white tea.

tea (noun)	herbal (noun)
a beverage made by steeping tea leaves in water	tea-like drink made of leaves of various herbs
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

tea (adjective)	herbal (adjective)
	of or relating to herbs