The Theravada school teaches the thirty one planes of existence.
These 31 planes are separated into three major categories:
- Immaterial or formless world (arupa loka)
- Fine material world (rupa loka)
- Sensuous world (kama loka)
The sensuous world is divided into:
- Happy destinations (including the human realm)
- Unhappy destinations (including hell and the animal realm)
The immaterial world has beings with mind but no body. This world is above or beyond the gods (brahmas and devas). The realms here include:
- Infinite Consciousness
- Infinite Space
It appears that devas (a type of god) and humans live in the happy sensuous destinations, while there are brahmas and devas (types of gods) living in the fine material world. Brahmas are superior to devas.
Those who have reached the level of non-returners (anagamin) would be reborn in the upper five realms of the fine material world. After this, they gain enlightenment there and would no longer be reborn, after passing.
All beings, whether formless beings or gods or humans or animals or ghosts etc. are not immortal. The gods like the Maha Brahmas may live for a very long period of time, that they may assume that they are immortal, according to DN11. All unenlightened beings would face death and rebirth, while enlightened beings would no longer be reborn after physical death.
The Buddha is said to be the highest type of being of them all, who is enlightened and has psychic powers allowing him to teach gods and humans in the fine material world and sensuous world. But even he is not immortal or permanent.
The only thing that is not impermanent is Nibbana. Udana 8.1 describes it as:
There is, bhikkhus, that base where there is no earth, no water, no
fire, no air; no base consisting of the infinity of space, no base
consisting of the infinity of consciousness, no base consisting of
nothingness, no base consisting of
neither-perception-nor-non-perception; neither this world nor another
world nor both; neither sun nor moon. Here, bhikkhus, I say there is
no coming, no going, no staying, no deceasing, no uprising. Not fixed,
not movable, it has no support. Just this is the end of suffering.