Hierarchy of Roman Catholic Church

1. The Pope has full and supreme power over the whole Church. If the college of bishops is united with the Pope as its head, the college has supreme and full authority over the whole Church. The Pope is the source of the unity of the bishops and of the whole Church. The pope assigns bishops to dioceses and transfers them to their dioceses.
2. A bishop is the shepherd of a diocese, assisted by priests and deacons. A bishop has the right to admit priests to his diocese, to assign them to parishes in his diocese and to exclude them from the practice of ministry within his diocese. The 'mother' church in a diocese is called a cathedral. In large dioceses, diocesan bishops may be assisted by auxiliary bishops. A coadjutor bishop is an auxiliary bishop who has the right of succession, e.g. he will replace the diocesan bishop in the event of death, transfer or retirement. A bishop Emeriti is a retired bishop, normally due to old age. A titular bishop is a bishop who has no geographical diocese, many of whom work in the Roman Curia.
3. A diocese is divided into parishes. A parish is is a community of the Christian faithful. The head of a parish is called a parish priest, whom is appointed by the bishop. In large parishes, parish priests may be assisted by other priests or deacons.
4. A cardinal is a bishop with additional functions of advising pope and electing a new pope. The Sacred College of Cardinals is the 2nd highest precedence in the Church. Unlike bishop, cardinal is not a hierarchical position. Cardinals are appointed by the Pope. Some cardinals are the chief members of the Sacred Congregations of the papal administration. Most cardinals are previously bishops, but if they are not, they are ordained bishop before being made cardinal. There are 3 grades of cardinals: episcopal, presbyteral and diaconal. Episcopal cardinals are the Titular Bishops of the 7 suburbicarian sees of Rome and Eastern Rite patriarchs. The Titular Bishop of Ostia is always the Dean of the Sacred College of Cardinals. Presbyteral cardinals are ordinary bishops (almost always metropolitans). Most cardinals are presbyteral. Diaconal cardinals are mainly the titular archbishops of the Roman Curia who have been raised to the Cardinalate. In 2001 there were 184 cardinals.
5. The Roman Curia [www.vatican.va/roman_curia] is the structure of the Rome government. It performs Pope duties in Pope's name with Pope's authority. It is divided into a collection of dicasteries: congregations, tribunals, pontifical councils, offices, agencies, commisions, vicariates and the secretary of state [www.vatican.va/roman_curia/secretariat_state].
6. The diocesan curia assist the bishop in the governing of the diocese. The vicars general are the auxiliary bishops of the diocese and one non-episcopal priest. Episcopal vicars are those priests who assit the ordinary in the governance of a specific geographic region of the diocese, which in turn is divided into vicariates forane. A vicariate forane is a collection of neighboring parishes for the promotion and coordination of pastoral activity. One of the parish pastors of the vicariate is named the vicar forane. Also part of the diocesan curia are the chancellor, vice-chancellor, and other diocesan notaries, whose job it is to record the decrees, dispositions, obligations, etc. A diocese normally has a finance council to handle the diocese's financial affairs and a presbyteral council, a group of priests who form a consultative body to advise the ordinary in matters of diocesan governance.
7. There are 4 types of archbishops: metropolitan, titular, coadjutor and emeritus. The last 3 are similar meaning to those of bishops. Metropolitan archbishops administer an ecclesiastical province as well as his own diocese. A province is a group of 2 or more dioceses. The dioceses which make up a province is called suffragans. His own diocese is called an archdiocese or metropolis. In his archdiocese his title is archbishop but in his provice his title is metropolitan.
8. A deacon is an ordained minister who assist the diocesan bishop and priests in various tasks, most importantly the celebration of the sacraments and the Mass. A transitional deacon is a seminarian studying for the priesthood. A permanent deacon can be married (?) and assists a priest by performing of the sacraments.
9. A monsignor is an honorary designation bestowed as an elevation from among the general ranks of the clergy. The honor is bestowed by the pope, typically at the request of diocesan bishops for one of their priests. By assuming the rank of monsignor, the priest is made a member of the “papal household.”

Source: Catechism of the Catholic Church, Code of Canon Law, Encarta Encyclopedia, Catholic Exchange, Acolyte Altar Servers Archive