The Animus is the machine that shows genetic memories in Assassin's Creed.
In the series, the Animus allows a person in the present day to experience memories inherited through an ancestor's genetic lineage. It provides the framework for visiting historical periods without treating the modern character as physically transported through time.
Desmond Miles uses an Animus in the first games, while later stories introduce other users and versions of the technology. The machine also lets the games connect historical missions with a continuing modern-day storyline.
The Animus is different from Eagle Vision, which is a perception ability, and from the Apple of Eden, an ancient Isu artifact. The Bleeding Effect is another separate concept: it describes skills or memories affecting an Animus user after repeated exposure.