18 For the nurturing and constant growth of the People of God, Christ the Lord instituted in His Church a variety of ministries, which work for the good of the whole body. For those ministers, who are endowed with sacred power, serve their brethren, so that all who are of the People of God, and therefore enjoy a true Christian dignity, working toward a common goal freely and in an orderly way, may arrive at salvation. This Sacred Council, following closely in the footsteps of the First Vatican Council, with that Council teaches and declares that Jesus Christ, the eternal Shepherd, established His holy Church, having sent forth the apostles as He Himself had been sent by the Father; and He willed that their successors, namely the bishops, should be shepherds in His Church even to the consummation of the world. And in order that the episcopate itself might be one and undivided, He placed Blessed Peter over the other apostles, and instituted in him a permanent and visible source and foundation of unity of faith and communion. And all this teaching about the institution, the perpetuity, the meaning and reason for the sacred primacy of the Roman Pontiff and of his infallible magisterium, this Sacred Council again proposes to be firmly believed by all the faithful. Continuing in that same undertaking, this Council is resolved to declare and proclaim before all men the doctrine concerning bishops, the successors of the apostles, who together with the successor of Peter, the Vicar of Christ, the visible Head of the whole Church, govern the house of the living God.
Source: Lumen Gentium (Vatican.va)