fairy ring vs halo

fairy ring and halo both are nouns.

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

As nouns, halo is a hypernym of fairy ring; that is, halo 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
halo: a toroidal shape

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

fairy ring (noun)	halo (noun)
a ring of fungi marking the periphery of the perennial underground growth of the mycelium	an indication of radiant light drawn around the head of a saint
	a circle of light around the sun or moon
	a toroidal shape