There are three Orders in the Church: the Order of Bishop, Priest, and Deacon. Which is why we call it the Sacrament of Holy Orders. The call them orders because they help to order our church life. All three are ordained. Bishops and priests are ordained to celebrate the Eucharist, preach, offer the sacraments, and lead the community. In addition, Bishops are ordained to lead the diocese, like the Archdiocese of Boston. Bishops and priests make three promises, sometimes mistakenly called vows: chastity for the sake of the kingdom, promise to pray the Liturgy of the Hours daily, and obedience to the local Bishop.
Deacons are different than priests or bishops. They are ordained for service. They can be married, but once they are ordained, they cannot get married or remarry. They must be married before they are ordained as deacons. They can baptize, marry outside of Mass, and bless things and people. They cannot celebrate Mass, hear confessions, or anoint the sick. At Mass, they lead the Penitential Rite, proclaim the Gospel, are permitted to preach, prepare the altar and the gifts, distribute communion, especially the cup, and give the dismissal at Mass.
Historically, the deacons were the ones who were responsible for caring for the poor, the sick, and the widowed in the Early Church. Alms for the poor would be given to the deacons who would then distribute them to the poor and the needy in the community. Meanwhile, the apostles and the early leaders would preach, heal the sick, and lead the Eucharist.
Today, deacons still do much of the work with the poor. In many parishes, deacons bring communion to the shut ins, work with the elderly, staff soup kitchens and food pantries, and offer work in parishes as business managers or finance people. Because of their experience as husbands and fathers, and their professional experience in their careers, their presence in modern day parish life is a real blessing.