The Sacrament of Holy Orders
All Christians share in Christ's priesthood.
All Catholics, indeed all Christians, share in the priesthood of Christ through their baptism into his death and resurrection.
In the New Covenant we have two kinds of priests. Those who have received the sacrament of Holy Orders and those who belong to the priesthood of the faithful (also called laity).
Priests offer sacrifice. That is their job: to be a mediator between God and man by offering sacrifice. This is very clear in the Old Covenant where the sacrifice offered is the blood of animals. In the New Covenant, Christ, the Lamb of God “entered once for all into the Holy Place, taking not the blood of goats and calves but his own blood” (Hebrews 9:12). The revelation of the Cross of Christ is that true love is sacrificial love. In this way Christ has offered an acceptable sacrifice to God the Father making it possible for the sacrifices of the faithful to participate in his one saving sacrifice.
Sacrifice is the center of Christian life because joined to the sacrifice of Christ...
the lives of the faithful, their praise, sufferings, prayer, and work are united with those of Christ and with his total offering, and so acquire a new value. (Catechism of the Catholic Church, 1368)
In the Church there are two different kinds of priesthood which “differ from one another in essence and not only in degree” (Vatican II, Dogmatic Constitution on the Church, 10). They are not two levels of priesthood, but are really different kinds of priesthood.
Jesus gave a profound gift to the eleven disciples who, except for John, had all betrayed Jesus at his passion.
breathed on then and said to them, ‘Receive the Holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained.’ (John 20:22-23)