Rebirth in the six realms is a central concept in Buddhism that describes the cycle of life, death, and rebirth (samsara) experienced by sentient beings. This cycle is influenced by karma, which refers to the actions and intentions that impact one's future existences. The six realms are categorized as gods, demi-gods, humans, animals, hungry ghosts, and hell beings, each representing different states of existence and experience based on the quality of one's karma.