"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."
From Catechism of the Catholic Church, Paragraph 1536, Retrieved from http://www.vatican.va/archive/ccc_css/archive/catechism/p2s2c3a6.htm
What is required to receive the sacrament?
To receive the sacrament, a man must go through a formation program and be called by either their bishop or superior in a religious order.
What should I do if I feel called explore a vocation as a priest or deacon?
Men who want to further explore a possible vocation to the priesthood or diaconate should pray about their vocation, read about the priesthood or diaconate, and should contact either their local priest or deacon or a vocation director of a diocese or religious order. If you would like to speak with one of the members of the clergy of the parish, please contact the office. If you would like to speak with the vocation director director for the Diocese of Harrisburg, Father Brian Wayne, please see the Diocese of Harrisburg's website for contact details.
How can I learn more about the sacrament?
The following links provide more information about the sacrament.
Holy Orders by Hubert Ahaus in The Catholic Encyclopedia via New Advent
Office of Vocations for the Diocese of Harrisburg