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. (Catechism of the Catholic Church #1536)
Holy Orders is the second Sacrament of Commitment and Service, in which a man promises or vows himself to the service of God and Church receiving the graces to minister the Sacraments and lead the Church in worship. The three orders or groups within the sacrament are Bishops, Priests and Deacons. Each Order has its particular duties and privileges.
Deacons are traditionally ministers of service. Married men can be ordained as deacons but if they are widowed they remain celibate and do not remarry. They can proclaim the Gospel at Mass, Baptize, assist the priest in the Eucharist, witness Sacramental Marriages, may preside at funeral liturgies without a Mass and often are involved in the care of the sick at homes and in hospitals.
Of the three orders of clergy Priests the most common. They minister predominantly in parishes, administering the sacraments of Baptism, Eucharist, Marriage, Reconciliation and the Anointing of the Sick. They preach at mass if a deacon is not present and usually have a ministry of general pastoral care for their congregations.
Bishops are the third of the Orders