Understanding the Structure and Roles Within a Catholic Diocese
The Diocese
At the forefront stands the Diocesan Bishop.
Auxiliary Bishop
It may happen that a bishop cannot fulfill the entrusted duties alone. If so, the diocese, at the request of their bishop, can count on one or more Auxiliary Bishops. For their selection, the head of the diocese will propose a list of at least three names to the Apostolic See. For its part, the Holy See may appoint a Coadjutor Bishop. The difference lies in the initiative of the appointment. Both, moreover, will be named Vicar General.
Diocesan Administrator
The Diocesan Administrator will govern the diocese temporarily. This figure gains importance and rationale when a seat becomes vacant. This happens in case of death, resignation, or removal of the Diocesan Bishop. At that time, a trustee will be appointed until the vacancy is filled. Normally, they should be elected by a board of consultants, although sometimes the Holy See appoints them, and they must have completed at least 35 years of age. Until the appointment of an administrator, the Auxiliary Bishop will govern the diocese, and if there is more than one, the one who is older in the order of promotion. The administrator ceases to hold office when a new bishop takes possession of the diocese.
Diocesan Synod
The Diocesan Synod is an assembly of priests and faithful who assist the bishop. The Bishop, Coadjutor or Assistant, the Vicar General, Episcopal and Judicial Canons of the Cathedral, and some lay faithful should be called. Also part of the synod are the Diocesan Seminary Rector, the Dean, a Presbyter of each senior Archbishopric, and some religious institutions. The synod is a purely consultative body.
The Diocesan Curia
The Diocesan Curia is a body that acts in cooperation with the bishop, especially in regard to pastoral, administrative, and judicial proceedings. It may have a Moderator who will coordinate the processing of administrative issues and assume the task of ensuring the rest of the staff of this body fulfill their duties. As a general rule, the Vicar General is usually appointed as the Moderator. Another of the positions belonging to the Curia is the Chancellor. Their main function is to ensure that records of the Curia are written and then kept in safe custody properly. They can count on the help of a Vice-Chancellor. The functions of the Chancellor (a figure that has disappeared, leaving only an honorary title) are usually carried out by the General Secretary of the Curia.
Vicars General and Episcopal Vicars
They must have reached their thirties. They are appointed and dismissed by the bishop, with consanguinity within the fourth degree being prohibited. The Vicar General exercises executive power vested in the diocese, while the Episcopal Vicar is concerned only with those issues or communities of faith, of a different rite, for which they are appointed. That is, the Episcopal Vicar figure is seen as an extension of the Vicar General, in that they are named in response to particular circumstances. We could talk of a Territorial Episcopal Vicar whose appointment involves taking over an area of the diocese, a Sector Episcopal Vicar, to address specific issues, and a Personal Episcopal Vicar, for assisting a group of people belonging to a particular rite. The general rule provides that only one Vicar General is named.