The device that lets users relive ancestral memories in Assassin's Creed is called the Animus.
The Animus is a fictional machine developed by Abstergo Industries. It allows a modern user to access genetic memories inherited from ancestors, presenting those memories as an interactive experience. Desmond Miles first uses the device in the original game to experience Altaïr's life.
The machine is central to the series' structure because it connects modern-day characters with historical protagonists. Later versions include the Animus Omega and portable or commercial variants, while the Helix platform is a related entertainment system seen in later stories.
The Animus does not literally send a person into the past. It reconstructs ancestral memories through fictional technology. Eagle Vision is an Assassin ability, and the Apple of Eden is an ancient artifact, so neither is the memory device itself.