Holy Orders is the sacrament by which bishops, priests and deacons are ordained and receive the power and grace to perform their sacred duties. The sacred rite by which orders are conferred is called ordination. The apostles were ordained by Jesus at the Last Supper so that others could share in his priesthood.
Called to Serve...
All people are called to serve God just as all people are called to holiness. A priest is called by God to serve in a very specific way as an alter Christus, another Christ.
The Catechism of the Catholic Church speaks of the priesthood: ¶1547 The ministerial or hierarchical priesthood of bishops and priests, and the common priesthood of all the faithful participate, "each in its own proper way, in the one priesthood of Christ." While being "ordered one to another," they differ essentially. In what sense? While the common priesthood of the faithful is exercised by the unfolding of baptismal grace --a life of faith, hope, and charity, a life according to the Spirit--, the ministerial priesthood is at the service of the common priesthood. It is directed at the unfolding of the baptismal grace of all Christians. The ministerial priesthood is a means by which Christ unceasingly builds up and leads his Church. For this reason it is transmitted by its own sacrament, the sacrament of Holy Orders.