Diocesan bishops—known as eparchs in the Eastern Catholic Churches—are assigned to govern local regions within the Catholic Church known as dioceses in the Latin Church and eparchies in the Eastern Churches. Bishops are collectively known as the College of Bishops and can hold such additional titles as archbishop, cardinal, patriarch, or pope. As of 2009 there were approximately 5,100 bishops total in the Latin and Eastern churches of the Catholic Church.
Bishops are always men. In addition, Canon 378 § 1 requires that a candidate for the Latin episcopacy should be:
The traditional role of a bishop is to act as head of a diocese or eparchy. Dioceses vary considerably in geographical size and population. A wide variety of dioceses around the Mediterranean Sea which received the Christian faith early are rather compact in size, while those in areas more recently evangelized, as in some parts of Sub-Saharan Africa, South America and the Far East, tend to be much larger and more populous. Within his own diocese a Latin Church bishop may use pontifical vestments and regalia, but may not do so in another diocese without, at least, the presumed consent of the appropriate ordinary.
Article 401.1 of the Latin-Rite Code of Canon Law states that "A diocesan Bishop who has completed his seventy-fifth year of age is requested to offer his resignation from office to the Supreme Pontiff, who, taking all the circumstances into account, will make provision accordingly". A motu proprio issued by Pope Francis on 15 February 2018 titled Imparare a congedarsi established a comparable rule for non-cardinal bishops serving in the Roman Curia, who had previously been required to retire at 75.
A "diocesan bishop" is entrusted with the care of a local Church (diocese). He is responsible for teaching, governing, and sanctifying the faithful of his diocese, sharing these duties with the priests and deacons who serve under him.