Samsara has the essential meaning of the cycle of rebirths or simply rebirth. Samsara is one of the key concepts in understanding the reason Hindu mythology can be so complex—figures changing genders from one lifetime to the next, rebirths in lifetimes with different names but carrying from a previous lifetime the results of actions not then completed, and teams of characters being reborn in new relationships or even in reversals of roles from previous lifetimes.
Rebirth was not a notion found in the early Vedic myths. There was a Vedic idea of redeath (punar mrityu). Eventually redeath became rebirth (punai avritti): the idea became prevalent that something would return to another life. But what returned and with how much memory of previous existences was the very essence of later mythology.