rockfoil vs herb

rockfoil and herb both are nouns.

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

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

rockfoil: any of various plants of the genus Saxifraga
herb: a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests

Other hypernyms of rockfoil include herbaceous plant.

rockfoil (noun)	herb (noun)
any of various plants of the genus Saxifraga	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