The world is divided into Heaven, the Netherworld, and the Mortal World, simply put, these are the Three Realms, the Heavenly Realm, the Netherworld, and the Mortal World.
There's no need to mention the Heavenly Realm, as I believe everyone understands that it is the domain of the various Celestial Courts and the Divine Race, the territory of the gods.
And the Netherworld is actually just a general term for the Netherworld; it refers to the Eastern Netherworld's Underworld or the Western Divine Court's Underworld. In any case, it's either filled with spirits, ghosts, or the Ghost Deities who rule over the Netherworld.
The Mortal World is even easier to explain, it's the place where humans reside.
