Short answers, pulled from the story.
Sañsāra is the beginningless cycle of repeated birth, mundane existence and dying again. Passages from the Samyutta Nikaya describe this process as fueled by ignorance and craving. The cycle lacks any particular direction or purpose until liberation occurs.
Buddhist cosmology typically identifies six distinct realms of rebirth including gods, demi-gods, humans, animals, hungry ghosts and hells. Earlier Buddhist texts refer to five realms rather than six realms when describing god and demi-god realms as a single category. These hellish regions include eight hot hells and eight cold hells where beings suffer intense pain before exhausting their unwholesome karma.
Outside of a Buddhist context, similar notions of cyclic existence date back to 800 BCE. Early Buddhist texts suggest the Buddha faced difficulty explaining what is reborn after inventing the concept of no self. Later scholars like fifth-century Pali scholar-monk Buddhaghosa suggested lack of self does not mean lack of continuity.
Sañsāra is perpetuated by karma resulting from intentional physical or mental acts causing future consequences. Whether a deed is wholesome or unwholesome determined by underlying intention known as cetana. Originally craving was considered root cause of samsara stilled by practice of dhyana leading to calm mind while later tradition considers ignorance to be root cause of samsara described as misconception about reality leading to grasping and clinging.
Sañsāra ends when one attains liberation identified with nirvana in early Buddhism. When this consciousness ceases then liberation is attained. There is connection between consciousness karmic activities and cycle of rebirth where destruction of consciousness leads to cessation of karmic activities necessary for continued perpetuation of cyclic existence.