The Sacrament of Holy Orders imparts to the one who is ordained a special character and grace to serve the Church in likeness to Christ.
While all members of the faithful, at Baptism are united to Christ in a likeness to his death and resurrection, and thus share in His priesthood (the priesthood of all believers), those who are ordained receive a special grace that is directed toward the guidance and service of the Church to live out this sense of union with Christ.
There three degrees of the Sacrament of Holy Orders.
The fullness of the Sacrament is received by those ordained to be bishops. Through a special outpouring and grace given by the Holy Spirit, the ordination of a bishop gives the one consecrated as a bishop the grace to stand in and live as a successor of the apostles. A bishop is graced with the work and mission of the apostles in the world today.
A priest is ordained in order to serve as a co-worker of the bishop. Priestly ordination confers a grace that allows the priest, in union with the bishops and the bishop of Rome, to serve and lead the Catholic Church throughout the world.
A deacon is ordained primarily to serve the Church. The deacon’s call is to give of self in a life of service by assisting the priests in performing Baptisms and witnessing marriages; at the Eucharistic table; and through other acts of service. There are two types of deacons:
A transitional deacon is a man who is ordained to the diaconate and serves as a deacon for a period of time prior to his ordination to the priesthood.
A permanent deacon is a man who is ordained to this life of service permanently.