spike moss vs club moss

spike moss and club moss both are nouns.

Word	Noun	Adjective	Verb	Adverb
spike moss	Yes	No	No	No
club moss	Yes	No	No	No

As nouns, club moss is a hypernym of spike moss; that is, club moss is a word with a broader meaning than spike moss:

spike moss: any of numerous fern allies of the genus Selaginella
club moss: primitive evergreen moss-like plant with spores in club-shaped strobiles

Other hypernyms of spike moss include club-moss, lycopod.

spike moss (noun)	club moss (noun)
any of numerous fern allies of the genus Selaginella	primitive evergreen moss-like plant with spores in club-shaped strobiles