fairy ring vs anchor ring

fairy ring and anchor ring both are nouns.

Word	Noun	Adjective	Verb	Adverb
fairy ring	Yes	No	No	No
anchor ring	Yes	No	No	No

As nouns, anchor ring is a hypernym of fairy ring; that is, anchor ring is a word with a broader meaning than fairy ring:

fairy ring: a ring of fungi marking the periphery of the perennial underground growth of the mycelium
anchor ring: a toroidal shape

Other hypernyms of fairy ring include annulus, doughnut, halo, ring.

fairy ring (noun)	anchor ring (noun)
a ring of fungi marking the periphery of the perennial underground growth of the mycelium	a toroidal shape