The six realms of rebirth

The six realms (Sanskrit ṣaḍgati, "six destinations") are a traditional list of where a being may be reborn within the cycle of birth and death. Your past actions (karma) incline you toward one or another. The six are often pictured as segments of a great wheel, and each can be read both as a literal rebirth-world and as a state of mind we pass through even now. (Some older lists count only five, folding the second realm below into the others; the six-fold version became the most familiar.)

The six, from most fortunate to least, are: (1) the gods (devas), long-lived heavenly beings enjoying great bliss; (2) the demigods or jealous titans (asuras), powerful but consumed by envy and conflict; (3) humans, a mixed life of pleasure and pain that is considered especially valuable because it offers the best chance to practice and awaken; (4) animals, driven by instinct, fear, and appetite; (5) the hungry ghosts (pretas), beings tormented by cravings they can never satisfy; and (6) the hell-beings, who undergo intense suffering until the karma that produced it is exhausted. Crucially, even these hells are not eternal; once the relevant karma runs out, the being is reborn elsewhere.

Two points keep this honest. First, none of these states is permanent or a final destiny, not even the heavens; the gods too eventually die and are reborn. Second, the moral isn't to chase a better realm but to step off the wheel entirely. Buddhism treats even the highest pleasant rebirth as still caught inside suffering's reach, so the realms together form a map of the predicament that awakening (nirvāṇa) is meant to resolve.