tea vs herbal tea

tea and herbal tea both are nouns.

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

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

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

tea (noun)	herbal tea (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