Jesus Christ, in offering Himself up for the sins of all mankind, fulfilled the duties of the Old Testament priesthood once and for all. But just as the Eucharist makes Christ’s sacrifice present to us today, so the New Testament priesthood is a sharing in the eternal priesthood of Christ. While all believers are, in some sense, priests, some are set aside to serve the Church as Christ Himself did.
The whole church is a priestly people.
Through Baptism all the faithful share in the priesthood of Christ.
This participation is called the “common priesthood of the faithful.”
Based on this common priesthood and ordered to its service,
there exists another participation in the mission of Christ:
the ministry conferred by the sacrament of Holy Orders,
where the task is to serve in the name and in the person of Christ the Head
in the midst of the community
Catechism of the Catholic Church #1591