The Pope Benedict XV is the successor of Saint Peter for our time
The Magisterium is the teaching authority of the Church. This is embodied in the Pope, Successor of Peter, first Bishop of Rome. Together with Him and under Him –Sub Petro, cum Petro-, presided by the Pope, the College of Bishops. Synods and Councils rally a group of bishops of the Church, under the Pope or His legates. As the saying goes: “Cum Petro, sum Petro”.
Saint Peter, the Apostle head of the Apostles, received the Keys from Jesus. The service of the Keys has since then been transmitted to the his successors, the Bishops of Rome.