An office or bureau of the Holy See, such as the Dicastery for the Doctrine of the Faith or the Dicastery for Divine Worship and the Discipline of the Sacraments. 

Prior to the reform of the Roman Curia promulgated by Pope Francis in Predicate evangelium (22 March 2022), the larger and more important departments were called Congregations, e.g. Congregation for the Doctrine of the Faith. 

Petrine refers to the unique office of St. Peter in the Church, and of the Bishop of Rome as his successor (Mt. 16:13-18). St. Peter was given the duty of confirming his brothers (the apostles) in the faith (Luke 22:32). Peter's successors, the Bishops of Rome, inherit this Petrine ministry to guard and confirm the unity of faith of his brothers, the bishops, and thereby all members of the Church. 

The legal weight and binding authority of the decisions of the Roman Curia comes from the will of the Supreme Pontiff. Canon 60 of the 1983 Code of Canon Law states: 

The Supreme Pontiff conducts the business of the universal Church by means of the Roman Curia, which fulfills its duty in his name and by his authority.

The 12 Apostles of Jesus Christ considered as a group. Also, their successors, the bishops of the Catholic Church, considered as a group. The apostles, taught by Christ, were individually able to expound revelation with authority, as St. Paul makes clear in 2 Thess. 2:15. Yet, sometimes they also acted as a college in union with Peter, as in the Council of Jerusalem (Acts 15). While the bishops do not have the individual charism the apostles had, when they teach or otherwise act with the Pope in a collegial act it carries the same weight. The most solemn cases of this are the dogmatic and judicial canons of the Ecumenical Councils. 

The Internal Forum is the arena of conscience. When a person reveals their interior life to a confessor in the Sacrament of Penance, to a spiritual director, or in similar situations with an expectation of complete confidence, it is said to be in the Internal Forum. The Church provides canonical sanctions for its violation, in the most severe case the automatic excommunication of a confessor who reveals information identifiable with a particular penitent.

On the other hand, the External Forum concerns matters of external ecclesiastical governance. Decisions in this forum have public effect, for example, the making of laws, and the punishment of their violation, or a decision about the validity of a marriage.

A See is a seat of authority, from the Latin sede. Jesus said the Pharisees sat on the chair of Moses (Mt. 23:2f). Judges sit on a bench, representing the authority of the state. Professors hold chairs of academic authority. And in the Church bishops possess chairs of spiritual authority. Thus, a diocese is called a See. 

The Roman diocese has been called the Apostolic See from ancient times. It is the seat of authority of the chief Apostle, Peter, and where the Apostles Peter and Paul were martyred. It is the Holy See, since its bishop has Christ’s authority over holy things. These expressions apply not only to the Pope, but also to those who assist him in governing the universal Church. [Code of Canon Law c. 361]