The virtual-reality device in the Assassin's Creed series is called the Animus.
The Animus lets a modern user access genetic memories inherited from ancestors. In the original game, Desmond Miles is placed in the machine by Abstergo Industries, allowing the company to make him relive the experiences of Altaïr Ibn-La'Ahad.
The device provides the narrative link between modern-day characters and historical settings. It explains why a single series can move from the Crusades to Renaissance Italy, the American Revolution, the Caribbean, ancient Egypt, and other eras while retaining a connected storyline.
Helix is a separate entertainment platform associated with later games, while Abstergo is the corporation operating the technology. Eagle Vision is an Assassin ability rather than a machine. These terms are often grouped together because they belong to the same fictional universe, but only Animus names the memory-replaying device.