In Assassin's Creed II, the Animus lets Desmond Miles relive Ezio Auditore's genetic memories. The machine interprets inherited memories encoded in Desmond's DNA and presents them as interactive experiences.
Desmond uses the Animus under the direction of Lucy Stillman and the modern Assassin team. Because he is descended from Ezio, the machine can access Ezio's experiences in Renaissance Italy, allowing Desmond to learn skills and uncover information needed in the present.
The Animus is a central piece of Assassin's Creed's science-fiction premise. It connects the modern-day storyline with historical settings without treating time travel as the explanation for the player's experience.
The Apple of Eden is a Piece of Eden, not the memory-viewing machine. The Bleeding Effect is a consequence of extended Animus exposure, through which users may retain abilities or behavioral traces from ancestral memories.