lobelia vs herb

lobelia and herb both are nouns.

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

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

lobelia: any plant or flower of the genus Lobelia
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 lobelia include herbaceous plant.

lobelia (noun)	herb (noun)
any plant or flower of the genus Lobelia	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