hellfire vs infernal region

hellfire and infernal region both are nouns.

Word	Noun	Adjective	Verb	Adverb
hellfire	Yes	No	No	No
infernal region	Yes	No	No	No

As nouns, infernal region is a hypernym of hellfire; that is, infernal region is a word with a broader meaning than hellfire:

hellfire: a place of eternal fire envisaged as punishment for the damned
infernal region: (Christianity) the abode of Satan and the forces of evil; where sinners suffer eternal punishment

Other hypernyms of hellfire include Hell, Inferno, nether region, perdition, pit.

hellfire (noun)	infernal region (noun)
a place of eternal fire envisaged as punishment for the damned	(Christianity) the abode of Satan and the forces of evil; where sinners suffer eternal punishment
	(religion) the world of the dead