The Animus is the device that lets modern users experience genetic memories in Assassin's Creed. It reads inherited memories encoded in a person's DNA and presents them as an interactive simulation.
The original game introduces Desmond Miles, who is forced to use the Animus so Abstergo Industries can investigate memories connected to his Assassin ancestors. The device gives the series a framework for moving between modern-day scenes and historical adventures.
The Animus does not literally send a person through time. Instead, it reconstructs ancestral experiences from genetic memory, allowing the user to perceive events through a simulated perspective. The games also use synchronization to represent how closely the player follows the ancestor's remembered actions.
Helix is another fictional technology associated with later Abstergo entertainment products, but it is not the general device introduced in the first game. Eagle Vision is a perception ability used by several protagonists, not a machine.