Holy Orders is the sacrament through which the mission entrusted by Christ to his apostles continues to be exercised in the Church until the end of time: thus it is the sacrament of apostolic ministry. It includes three degrees: episcopate, presbyterate, and diaconate. – The Catechism of the Catholic Church 1536
In order to shepherd the People of God and to increase its numbers without cease, Christ the Lord set up in his Church a variety of offices which aim at the good of the whole body. The holders of office, who are invested with a sacred power, are, in fact, dedicated to promoting the interests of their brethren, so that all who belong to the People of God… may attain to salvation. – The Catechism of the Catholic Church 874
For more information please visit the Archdiocese Office of Vocations.