The Animus is the technology in Assassin's Creed that lets users relive genetic memories.
In the series, the Animus is a machine that reads inherited memories encoded in a person's DNA. A present-day user enters the device and experiences the life of an ancestor, allowing the games to move between modern settings and historical periods.
Desmond Miles is the first major modern character shown using the Animus. Abstergo Industries initially presents the machine as a tool for memory research, but the device is also connected to the Templars' search for powerful artifacts and strategic information.
The Animus does not literally send a person through time. It reconstructs ancestral experiences from genetic memories, while the fictional Bleeding Effect explains why repeated use can influence the user's skills and behavior. Eagle Vision is a perception ability, and an Apple of Eden is a Piece of Eden, not a machine.