Churches with an episcopal polity are governed by bishops, practicing their authorities in the dioceses and conferences or synods. Their leadership is both sacramental and constitutional; as well as performing ordinations, confirmations, and consecrations, the bishop supervises the clergy within a local jurisdiction and is the representative both to secular structures and within the hierarchy of the church. Bishops are considered to derive their authority from an unbroken, personal apostolic succession from the Twelve Apostles of Jesus.