Therefore, priests are called to prolong the presence of Christ, the one high priest, embodying his way of life and making him visible in the midst of the flock entrusted to their care...
In the Church and on behalf of the Church, priests are a sacramental representation of Jesus Christ - the head and shepherd - authoritatively proclaiming his word, repeating his acts of forgiveness and his offer of salvation - particularly in baptism, penance and the Eucharist, showing his loving concern to the point of a total gift of self for the flock, which they gather into unity and lead to the Father through Christ and in the Spirit.
In a word, priests exist and act in order to proclaim the Gospel to the world and to build up the Church in the name and person of Christ the head and shepherd.
Pope John Paul II
Pastores dabo vobis 15