The Sacrament of Holy Orders
By the power of the Holy Spirit, the Risen Christ continues to lead His flock here on earth through the ministerial priesthood ordained for this purpose through the Sacrament of Holy Orders. This particular sacrament is called 'orders' because there are three participatory degrees to this sacrament, all 'ordered' to one another. The three orders are bishop, priest and deacon; all ordered to serve in distinct yet interconnected ways. We are all by our baptism part of the common priesthood of Jesus Christ, but from among the faithful some are chosen for the ministerial priesthood and 'ordered' in a special way to be at service of the common priesthood. The ordained priesthood is a means by which Jesus Christ builds up and leads His Church here on earth (CCC 1544-1547).
Fr. Chris Lemieux, former Director of Vocations for the archdiocese offers this:
Priests are men specially chosen from among the People of God and the faithful to proclaim the 'Good News' of salvation to all the world, as Jesus Christ gave this mission to the Apostles and disciples in a special way and commissioned them to continue this part of the mission. The mission is given to all of us through our baptism, but the priest serves and leads us in this mission. By the Sacrament of Holy Orders and the Power of the Holy Spirit, priests gather with the people and lead them in worship, celebrating for us all the Sacrament of the Eucharist, the source and summit of our faith, the Holy Mass. Priests are given the task of reaching out to "the scattered" those who have left or feel rejected in their faith. They build up the Body of Christ by welcoming new members through baptism. Priests are given healing powers; to forgive sins in the name of Christ through the Sacrament of Reconciliation and anointing the sick. In general, the priest allows the people a direct and personal encounter with Jesus Christ at the most important moments of their lives through the Sacraments.
To learn more about vocations through the Sacrament of Holy Orders, these resources may help:
Catechism of the Catholic Church (1536-1600)
Compendium of the Catechism of the Catholic Church: Holy Orders (321-336)
Code of Canon Law (cc. 232-293)