What are/who are the Silence

The Silence was a religious order who considered themselves the “Sentinels of History”. They tried to kill the Doctor because of a specific prophecy, which stated: “On the fields of Trenzalore, at the fall of the eleventh, when no living creature can speak falsely or fail to answer, a Question will be asked, a question that must never, ever be answered.”

The Question was the “The First Question, the oldest question in the Universe, that must never be answered, hidden in plain sight.” Dorium Maldovar told the Eleventh Doctor that the question was: “Doctor Who?”, which was a question the Doctor had been apparently running from his entire life/lives.

Simple as that. =)

The silence was a race that made you forget any contact you had with them when you look away you fotget about them, don,t turn your back