As Vicar of Jesus Christ, the Pope governs the Catholic Church as its supreme head. The Pope, as Bishop of Rome, is the chief pastor and shepherd of the whole Church. We believe that the Pope is the successor of Peter, and his bishops are successors of the Twelve Apostles.
It is clear throughout that it is a question of the bishops acting in conjunction with their head, never of the bishops acting independently of the Pope. In the latter instance, without the action of the head, the bishops are not able to act as a College: this is clear from the concept of "College." This hierarchical communion of all the bishops with the Supreme Pontiff is certainly firmly established in Tradition. (Lumen Gentium, Note of Explanation)
In the Acts of the Apostles, we come to know Peter is the head of the early church. When Peter is given the “keys to the kingdom,” Christ is establishing the divine office of leadership over the church. The permanence of the office of the Pope is essential to the everlasting nature of the church.
Unity is essential for the followers of Jesus. John’s gospel reminds us, “The glory which You have given Me I have given to them, that they may be one, just as We are one; I in them and You in Me, that they may be perfected in unity, so that the world may know that You sent Me, and loved them, even as You have loved Me.” (John 17:22-23)
The Catholic Church is united under the leadership of the Bishop of Rome, the Pope. Historical breaks and schisms have left us fractured, with the Eastern Orthodox churches no longer in full unity with Roman Catholicism. Beginning with John XXIII and continuing through the papacy of John Paul II and our current pope, the movement to come together in full Christian unity has been underway.