The Animus is the machine that lets users experience genetic memories in Assassin's Creed.
In the series' science-fiction framework, the device reads inherited memories encoded in a person's DNA. A modern subject lies inside the Animus while the system reconstructs an ancestor's experiences as an interactive simulation.
The machine provides the link between modern-day characters and historical protagonists such as Altaïr Ibn-La'Ahad, Ezio Auditore, and Edward Kenway. It also explains why the games can move between different centuries while retaining a continuing narrative.
The Animus is not the same as Eagle Vision, which is a perception ability, or the Apple of Eden, which is an Isu artifact. The Bleeding Effect is a consequence of prolonged Animus exposure, not the machine itself.