"Vocation does not come from a voice "out there" calling me to be something I am not. It comes from a voice "in here" calling me to be the person I was born to be."
All Christians are called to be a gift of self to one another, and not just with family members and friends. Some of us are also called by God to be total gift of self to the People of God, the Church - as prayerful catalysts of spirituality and active-love among other disciples of Jesus Christ.
Holy Orders is the sacrament through which the mission entrusted by Christ to his apostles is exercised in the Church until the end of time. It is the sacrament of apostolic ministry. It includes three degrees: episcopate, presbyterate and diaconate.
A Bishop, by virtue of his ordination, is the direct successor of the Apostles. His principle task is to teach, sanctify and shepherd the members of the Church.
A Presbyter (or priest) is ordained to assist the bishops in their ministry, and are tasked with celebrating the Eucharist, administering the Sacraments and spreading the Good News.
A Deacon is ordained to assist the bishops and priests. They assist at the Eucharist, distribute Holy Communion, baptize, bless marriages, proclaim and preach the Gospel, preside over funerals and above all, dedicate themselves to ministries of charity.