Desmond Miles is the modern-day protagonist in the original Assassin’s Creed series arc.
Desmond is a bartender who is abducted by Abstergo Industries and forced to use the Animus. The machine lets him access genetic memories inherited from his ancestors, including Altaïr Ibn-La'Ahad, Ezio Auditore, and Connor Kenway.
Through these memories, Desmond learns about the long conflict between the Assassins and Templars while searching for information connected to powerful Pieces of Eden. His modern-day storyline links otherwise separate historical campaigns into one continuing narrative.
Desmond’s arc is especially prominent from the first game through Assassin’s Creed III. Later games generally use different modern protagonists or less individually defined employees, which is why players sometimes confuse Desmond with William Miles, his father, or with the historical characters whose memories he experiences.