estragon vs herb

estragon and herb both are nouns.

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

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

estragon (noun)	herb (noun)
fresh leaves (or leaves preserved in vinegar) used as seasoning	aromatic potherb used in cookery for its savory qualities
aromatic perennial of southeastern Russia	a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests