tea leaf vs herb

tea leaf and herb both are nouns.

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

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

tea leaf (noun)	herb (noun)
dried leaves of the tea shrub; used to make tea	aromatic potherb used in cookery for its savory qualities
	a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests