The highest order of ordained ministry in Catholic teaching is that of bishop. Most bishops are diocesan bishops, the chief priests in their respective dioceses. But some (auxiliary bishops) are the top assistants to their diocesan bishops, and some priests are made bishops because of special posts they hold in the church, such as certain Vatican jobs. Diocesan bishops and their auxiliaries are responsible for the pastoral care of their dioceses. In some cases diocesan bishops are assigned a coadjutor bishop, who is like an auxiliary except that he automatically becomes the diocesan bishop when his predecessor resigns or dies. In addition to their diocesan responsibilities, all bishops have a responsibility to act in council with other bishops to guide the church. In Eastern Catholic churches, an eparchy is equivalent to a diocese in the Latin Church, and eparch is equivalent to bishop.
The title given automatically to bishops who govern archdioceses is archbishop. The title "archbishop" is also given to certain other high-ranking church officials, notably Vatican ambassadors (apostolic nuncios), the secretaries of Vatican congregations and the presidents of pontifical councils.
The chief diocese of an Eastern Catholic ecclesiastical province is an archeparchy and is led by an archeparch, who is equivalent to an archbishop in the Latin Church. There are only two Catholic archeparchies in the United States: the Byzantine Catholic Archdiocese of Pittsburgh and the Ukrainian Catholic Archdiocese of Philadelphia.