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. It is the sacrament of apostolic ministry and includes three degrees: episcopate, presbyterate and diaconate.
By divine institution, the sacrament of Holy Orders establishes some among the Christian faithful as sacred ministers through an indelible character that marks them. They are consecrated and designated, each according to his grade, to nourish the people of God, fulfilling the functions of teaching, sanctifying and governing.
For more details, see the Catechism of the Catholic Church, starting at 1536 to 1600.