bog moss vs moss

bog moss and moss both are nouns.

Word	Noun	Adjective	Verb	Adverb
bog moss	Yes	No	No	No
moss	Yes	No	No	No

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

bog moss: any of various pale or ashy mosses of the genus Sphagnum whose decomposed remains form peat
moss: tiny leafy-stemmed flowerless plants

bog moss (noun)	moss (noun)
any of various pale or ashy mosses of the genus Sphagnum whose decomposed remains form peat	tiny leafy-stemmed flowerless plants