“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.” 1
Within the Old Covenant, God instituted a priesthood that was set aside to lead liturgical worship and sacrifice. The the Law and its sacrifices were powerless to bring about salvation, but served as a tutor to prepare God’s people for the perfect and complete sacrifice of Christ.”2 It also served as a prototype for liturgical worship in the Church, to be fulfilled with Christ as High Priest forever.”3 As Christ prepared for His ascension, He commissioned His apostles to continue His work–not as mediators of the imperfect and temporary Old Covenant, but as vessels for His presence, authority, and supernatural power in the eternal New Covenant.”4 Through apostolic succession, clergy in the Church have the authority to administer sacraments, teach, and provide pastoral care.” 5,6
There are three ranks within the sacrament of holy orders: bishops, priests, and deacons.7 This ministry is a special calling and gift from God.
Religious orders are distinguished from holy orders in that the former is a cloistered community in which members live a contemplative life of service. Religious orders are not a sacrament, but like holy orders they are a special calling and gift from God.
The US Conference of Catholic Bishops has many resources to help men discern if this is their calling.