Saṃsāra in Buddhism, states Jeff Wilson, is the “suffering-laden cycle of life, death, and rebirth, without beginning or end”. Also referred to as the wheel of existence (Bhavacakra), it is often mentioned in Buddhist texts with the term punarbhava (rebirth, re-becoming); the liberation from this cycle of existence, Nirvana, is the foundation and the most important purpose of Buddhism.
Samsara is considered impermanent in Buddhism, just like other Indian religions. Karma drives this impermanent Samsara in Buddhist thought, states Paul Williams, and “short of attaining enlightenment, in each rebirth one is born and dies, to be reborn elsewhere in accordance with the completely impersonal causal nature of one’s own karma; This endless cycle of birth, rebirth, and redeath is Saṃsāra”. The Four Noble Truths, accepted by all Buddhist traditions, are aimed at ending this Samsara-related re-becoming (rebirth) and associated cycles of suffering.
Like Jainism, Buddhism developed its own Samsara theory, that evolved over time the mechanistic details on how the wheel of mundane existence works over the endless cycles of rebirth and redeath. In early Buddhist traditions, Saṃsāra cosmology consisted of five realms through which wheel of existence recycled. This included hells (niraya), hungry ghosts (pretas), animals (tiryak), humans (manushya), and gods (devas, heavenly). In latter traditions, this list grew to a list of six realms of rebirth, adding demi-gods (asuras). The “hungry ghost, heavenly, hellish realms” respectively formulate the ritual, literary and moral spheres of many contemporary Buddhist traditions.
The Saṃsāra concept, in Buddhism, envisions that these six realms are interconnected, and everyone cycles life after life, and death is just a state for an afterlife, through these realms, because of a combination of ignorance, desires and purposeful karma, or ethical and unethical actions. Nirvana is typically described as the freedom from rebirth and the only alternative to suffering of Samsara, in Buddhism. However, the Buddhist texts developed a more comprehensive theory of rebirth, states Steven Collins, from fears of redeath, called amata (death-free), a state which is considered synonymous with nirvana. (Source: Wikipedia)