Jesus chose 12 men to be apostles. After Jesus' ascension, the apostles had the critical mission of spreading the news about Jesus. The apostles then chose a new Church leader to be a witness to Jesus Christ and continue his work. The pope and bishops, esteemed successors to the apostles, have been called and decided to continue Jesus' work.
The Sacrament of Holy Orders stands apart as the sacrament through which the mission entrusted by Christ to his apostles is perpetuated in the Church until the end of time. It is a sacrament of apostolic ministry, unique in its role and significance. This sacred sacrament is structured into three distinct degrees: episcopate (bishop), presbyterate (priest), and diaconate (deacon).
While all members of the Church partake in the priesthood of all believers through Baptism, there exists a fundamental difference between this common priesthood and the ministerial priesthood. The ministerial priesthood, in its essence, bestows a sacred power for the service of the faithful, setting it apart from the common priesthood of the faithful.
However, some men are called to serve Jesus and the Church today by celebrating the Sacrament of Holy Orders. Through their leadership in the Church, they help continue Jesus' presence on earth in the tradition of the apostles. The ordained ministers exercise their service for the People of God by teaching (munus docendi), divine worship (munus liturgicum), and pastoral governance (munus regendi). (Catechism of the Catholic Church, #1592)
Those who are called to be priests are ordained through the Rite of Ordination. In celebrating this Rite, men receive a permanent spiritual mark, called a character, signifying that they represent Jesus' presence in the Church. There are three levels of participation in the Sacrament of Holy Orders: bishop, priest (from presbyter, which is Greek for "elder"), and deacon.
A bishop receives the fullness of the Sacrament of Holy Orders. He is the head or Ordinary of the local Church. The local area entrusted to him is called a diocese. A bishop is also a member of the episcopal college: all the bishops who, with the pope, guide the Church.
Priests serve the community in various ways. They may be called to serve in their dioceses or as religious order priests, carrying out the mission of a particular religious community. They preside at liturgies, preach, administer the sacraments, counsel people, serve as pastors, and teach.
Deacons help and serve bishops by serving the Church's needs, proclaiming the gospel, teaching and preaching, baptizing, witnessing marriages, and assisting the priest celebrant at liturgies. Deacons are ordained for service in the Church. Some are studying to become priests, and others, including married men, are called to remain deacons for life and serve the Church in this capacity, a testament to their unwavering dedication.
Priests receive the Sacrament of Holy Orders in the Rite of Ordination. The bishop lays his hands on the candidate's head and says a prayer, asking for the outpouring of the Holy Spirit. In one part of the Rite, the candidate lies before the altar while the Litany of the Saints is sung or recited. A priest's hands are anointed with chrism in another part of the Rite. The new bishop's head is anointed in the Rite for a bishop.
Ordination to the priesthood is always a call and a gift from God. Christ reminded his Apostles that they needed to ask the Lord of the harvest to send laborers into the harvest. Those seeking priesthood respond generously to God's call using the prophet's words, "Here I am, send me" (Is 6:8).