The Sacrament of Holy Orders consists of deacons, priests, and bishops. The diaconate is the first level of Holy Orders whereby a man is ordained a deacon.
The second level is the priesthood, and the third is the episcopate, where a priest is ordained a bishop. To become a bishop, a man must have previously been ordained as a priest, and to become a priest, a man must have previously been ordained as a deacon. Not all deacons become priests, however, just as not all priests become bishops.
While these three levels of Orders exist within the Church, there are more designations and subdivisions which are not part of Holy Orders per se in that they are not derived from the Sacrament. The hierarchy of the Catholic Church uses the ordained ministry since Canon Law stipulates only someone in Holy Orders (called a cleric, whether a deacon, priest, or bishop) can exercise governance in the Church.
The clergy have the right, the duty, and the obligation to govern the Church while the laity are empowered to govern the secular world, especially in terms of government. Clergy are now prohibited from holding public office since that is the proper arena of laity. Likewise, only clergy (ordained deacons, priests, or bishops) can be named as pastors of parishes since the role involves ecclesiastical governance, which is the proper arena of clergy.
At the lowest level of the hierarchy are the deacons (permanent and transitional) and the parochial vicars (priests who help the pastor). Newly ordained priests (formerly called curates, assistant pastors, or associate pastors) are first assigned to a parish with the title of parochial vicar. The parochial vicar, along with any deacons assigned in that parish, provides assistance to the pastor by helping teach religion class, visiting the sick and bringing them Holy Communion, baptizing infants, preparing couples for marriage, performing the marriage ritual, conducting wake services and burial rites for the deceased, celebrating Benediction of the Blessed Sacrament, and preaching the homily at Mass.
The pastor is the priest assigned by the local bishop to care for the entire parish. He determines the time of the Masses, assigns the parochial vicar and deacon their duties, and signs the checks. Pastors have ordinary jurisdiction, which means they can baptize and marry any Catholic who lives in the territory of the parish. A parish is usually a geographical area comprised of several neighborhoods. An exception would be an ethnic or national parish; for example, an African American, Italian, or Polish parish where the language or culture is what defines membership rather than zip code.
Most parish pastors are diocesan priests and some are also titled Monsignor, an honor given by the pope for personal recognition. The parish pastor, whether a Monsignor or just a priest, is the one responsible for the spiritual and temporal welfare of the parish. Canon Law provides for the assistance of parochial vicars, deacons, and a parish council and a finance committee (both of which have no deliberative authority, but are consultative, giving advice and counsel to the pastor).
Several parishes in an area are usually designated as a deanery, and the dean is the priest given the responsibility of reporting and communicating matters of concern between the parishes and pastors of the deanery and the local bishop. The dean has no authority over the local pastors, but if one of them is derelict in his duties, the dean is to report this to the bishop and can then inform the pastor of the bishop’s response.
Once Christianity became legal in the Roman Empire in 313 AD, the Church embraced the Roman system of law and imperial order to help govern a growing and soon-to-be worldwide religion. Hence, the designation of local pastors and parishes, deans and deaneries, bishops and dioceses, and so on often resembles the Roman model of the provincial delineation of authority.
All the deans of a diocese meet regularly with the local Bishop, who is considered the pastor of the diocese. A diocese is a geographical area, like a deanery, except that the borders are determined by the Vatican. Each bishop defines the area of deaneries and parishes since they fall within the boundaries of his jurisdiction.
Bishops are appointed by the pope and have authority over all the parishes, parochial schools, and associations (hospitals, nursing homes, and so on) that lie within their territory. The pope can send him a personal helper called an auxiliary bishop who can ordain and confirm but who has no power to govern outside of what he is specifically entrusted with by the local bishop. Bishops also have a vicar general and chancellor to help in the daily business of the diocese. There are also the College of Deans, the Board of Consulters, the Presbyteral Council, the Personnel Board, and the Finance Board which offer advice and counsel but have no deliberative authority of their own.
Several dioceses in a geographical region also comprise what is called a province, and that is led by the metropolitan archbishop of the nearest archdiocese. Like the dean, who keeps an eye on the parishes in his deanery and reports any problems to the bishop, the metropolitan does not directly interfere with the regular business of the local bishops, but does intervene if one misbehaves, in which case the matter is reported to Rome. Every five years, the bishops of the same province go to Rome for the ad limina visit, which is an official meeting with the pope and each local bishop to explain how things are going. The bishops of a country or nation assemble once or twice a year in an episcopal conference to discuss areas of concern, to network with each other, and occasionally to issue some guidelines for their people; in the USA, this is the USCCB (United States Conference of Catholic Bishops).
Every nation has a personal representative of the pope who acts as the papal ambassador to that country, and his residence is the equivalent of a foreign embassy. Countries that do not have diplomatic relations with Vatican City have apostolic delegates that represent the pope to the head of state and to the local bishops of that country. Where there is diplomatic recognition (via treaty or concordat), the papal ambassador is called the apostolic nuncio, and his embassy is called the nunciature.
In addition to his diplomatic role with the national government, the nuncio also gathers names from which the pope selects bishops for that nation. He also reports any serious problems which need to be made known to the Holy Father.
The Vatican has various cardinals who help administrate the global and universal church. The curia and all the preceding elements of the hierarchy help in the governance of the Catholic Church.