Episcopal polity is a form of church governance that is hierarchical in structure with the chief authority over a local Christian church resting in a bishop. This episcopal structure is found in the ancient Churches: in the various churches of Roman Catholic, Eastern Orthodox and other Eastern Church lineage, and also those of Anglican lineage. Some churches founded independently of these lineages also employ this form of church governance.
The word episcopal is derived from the Greek: επίσκοπος, transliterated epískopos, which literally means overseer; the word, however, is used in religious contexts to refer to a bishop.
Churches having episcopal polity are governed by bishops, who have authority over dioceses, conferences, or synods (in general referred to as a judicatory). Their presidency is both sacramental and political; as well as performing ordinations, confirmations, and consecrations, the bishop supervises the clergy within the judicatory and is the representative to both secular structures and in the hierarchy of the church. It is usually considered that bishops derive their authority from an unbroken, personal Apostolic Succession from the Twelve Apostles of Jesus. Bishops with such authority are known as the historical episcopate. Churches with this type of government usually believe that the Church requires episcopal government as described in the New Testament.
In some systems, bishops may be subject to higher-ranking bishops (variously called archbishops, metropolitans, and/or patriarchs, depending upon the tradition). They also meet in councils or synods. These gatherings, subject to presidency by higher ranking bishops, may govern the judicatory which are represented in the council, though the synod or council may also be purely advisory.
For much of the written history of Christianity, episcopal government was the only known form of church organization. This changed at the Reformation. Many Protestant churches are now organized by either congregational or presbyterian church polities, both descended from the writings of John Calvin, a Protestant reformer working and writing independently following the break with the Roman Catholic Church precipitated by The Ninety-Five Theses of Martin Luther.
Read more about Episcopal Polity: Overview of Episcopal Churches, Before The Great Schism, Roman Catholic Church, Eastern Orthodox Church, Oriental Orthodox Churches, Anglican Communion, Methodist Churches, Episcopal Government in Other Denominations