- from CatholicCulture.org
A diocese is the territory in which a particular bishop has jurisdiction. They grew out of the Roman Empire, which divided its provinces into smaller diocese for ease of administration. As the Christianity became the official religion of the empire, Bishops began to assume administrative roles alongside their civil counterparts. When the Western empire fell, these bishops continued to perform these roles with the diocese as the main level of administration. Today, diocese serve as the main connection between individual parishes and the larger universal Church. Bishops are given great authority within their diocese and are often the highest Church official the average Catholic has contact with. In addition to the diocese, the Church also creates archdiocese which are often the most important diocese within an ecclesiastical province and whose bishop has limited authority over the other diocese within the province.