pearl-weed vs ground cover

pearl-weed and ground cover both are nouns.

Word	Noun	Adjective	Verb	Adverb
pearl-weed	Yes	No	No	No
ground cover	Yes	No	No	No

As nouns, ground cover is a hypernym of pearl-weed; that is, ground cover is a word with a broader meaning than pearl-weed:

pearl-weed: any of various low-growing plants of the genus Sagina having small spherical flowers resembling pearls
ground cover: low-growing plants planted in deep shade or on a steep slope where turf is difficult to grow

Other hypernyms of pearl-weed include groundcover.

pearl-weed (noun)	ground cover (noun)
any of various low-growing plants of the genus Sagina having small spherical flowers resembling pearls	small plants other than saplings growing on a forest floor
	low-growing plants planted in deep shade or on a steep slope where turf is difficult to grow