“Today, we’re announcing more details on the structure of the Oversight Board and its relationship to Facebook in the form of a charter. This central governing document defines the board’s mandate and describes its relationship to Facebook. It establishes its membership, governance and decision-making authority, and it sets out parameters for things like the size, scope and power of the board. In the coming months this charter will be available in multiple languages on a new board website.”
Source : Establishing Structure and Governance for an Independent Oversight Board | Facebook Newsroom