10 Christ the Lord, High Priest taken from among men, made the new people "a kingdom and priests to God the Father". The baptized, by regeneration and the anointing of the Holy Spirit, are consecrated as a spiritual house and a holy priesthood, in order that through all those works which are those of the Christian man they may offer spiritual sacrifices and proclaim the power of Him who has called them out of darkness into His marvelous light. Therefore all the disciples of Christ, persevering in prayer and praising God, should present themselves as a living sacrifice, holy and pleasing to God. Everywhere on earth they must bear witness to Christ and give an answer to those who seek an account of that hope of eternal life which is in them. Though they differ from one another in essence and not only in degree, the common priesthood of the faithful and the ministerial or hierarchical priesthood are nonetheless interrelated: each of them in its own special way is a participation in the one priesthood of Christ. The ministerial priest, by the sacred power he enjoys, teaches and rules the priestly people; acting in the person of Christ, he makes present the Eucharistic sacrifice, and offers it to God in the name of all the people. But the faithful, in virtue of their royal priesthood, join in the offering of the Eucharist. They likewise exercise that priesthood in receiving the sacraments, in prayer and thanksgiving, in the witness of a holy life, and by self-denial and active charity.
Source: Lumen Gentium (Vatican.va)