The Seven Sacraments
Christ instituted the sacraments of the new law:
Baptism, Confirmation, the Eucharist, Penance, the Anointing of the Sick, Holy Orders and Matrimony.
The Sacrament of Apostolic Ministry
Christ entrusted the mission of the Church to his apostles to be continued until the end of time. The Sacrament of Holy Orders
consecrates men to feed the Church by the word and grace of God. Holy Orders includes three degrees: episcopate (bishop), presbyterate (priest), and diaconate (deacon).
Holy Orders (Catechism of the Catholic Church)
The apostles imparted the gift of the Spirit by the laying on of hands. Bishops continue the tradition; as successors of the apostles, they consecrate men in the mission of the Church.
The order of bishop represents the fullness of the Sacrament of Holy Orders. Episcopal consecration confers the threefold office of sanctifying, teaching, and governing. In the model of Christ, bishops serve as teachers, shepherds, and priests; they act as Christ's representatives. Bishops are to be true and authentic teachers of the faith -- pontiffs and pastors. Bishops exercise authority in communion with the whole college of bishops, under the guidance of the Pope, the Bishop of Rome.
Christus Dominus (Second Vatican Council)
Bishops ordain priests to be their co-workers in fulfilling the apostolic mission of Christ. Priests make their bishop present to individual congregations; they exercise their priestly ministry in communion with their bishop and under his authority.
Priests are anointed, signed with a special character, and configured to Christ the High Priest. They are consecrated to preach the Gospel, shepherd the faithful, and celebrate divine worship.
When priests celebrate the holy sacrifice of the Mass, they act in the person of Christ. In the mystery of the Eucharistic Sacrifice, priests fulfill their greatest duty, perpetuating the work of our redemption.
Priests gather together God's family and lead them in the Spirit, through Christ, to God the Father. They are called to serve the people of God, assisting their bishop in the building up of the whole body of Christ.
Presbyterorum Ordinis (Second Vatican Council)
Deacons are ordained to the service of the liturgy, of the Gospel, and of works of charity. In communion with the bishop and his presbyterate, deacons are invested with a sacred power and raised to a sacred Order.
Deacons are not lay people. They represent a lower level of the Church's hierarchy, and they are charged to speak to the community in the name of Christ.
Deacons receive the obligation of ministerial service. As "slaves of Christ," they perform works of assistance, proclaim the Scriptures, instruct the people, administer Baptism, distribute the Eucharist, assist at and bless marriages, administer Viaticum to the sick, assist and preside at the rites of funeral and burial, and administer sacramentals.
After the priest, the deacon is given first place among those who minister in the celebration of the Eucharist.
Men aged 36 or older, whether single or married, may be called to the diaconate. Once a man has received the order of deacon, he may not enter into marriage.
Like bishops and priests, deacons are indelibly marked with a distinguishing sign impressed on the soul. Their sacred ordination is for life.
Sacrum Diaconatus Ordinem (Second Vatican Council)