Bishop is the English version of the Greek word επισκοπος (episkopos), which means overseer or supervisor. (Note the progression from episkopos to pickup to bishop.) The qualifications for bishops are given in 1 Timothy 3, but there is no scriptural description of their duties. In the middle of the first century, the local church, and the churches founded by its bishop, were headed by a bishop and the priests served as a board of advisors who also functioned as clergy under the bishop’s direction. By the time of Ignatius at the end of the first century, the Church had grown. By that time, bishops had territorial supervision over several churches, while the presbyters were responsible for pastoral care of individual churches. Ignatius describes a system identical to the modern practice, well in accord with Titus 1:6-9 and the situation in the seven letters in Revelation. Bishops wear purple clericals.
Apparently the apostles had the strategy of evangelizing major urban areas, with the intent that those churches would evangelize the surrounding areas. The New Testament mentions the church at Ephesus, the largest city in the Roman province of Asia (now part of southwestern Turkey), but does not mention the nearby smaller city of Magnesia. In AD 117, Ignatius passed through the same area and was greeted by the bishop of Magnesia, from a church that had been founded after Paul left and before Ignatius arrived.
In the historic church, a bishop is a regional minister, a priest with administrative duties over a group of churches in a territory called a diocese. Only bishops can preside at the rite of ordination. An individual bishop can ordain a deacon or a priest, but it takes three bishops to consecrate a new bishop. A Roman Catholic bishop must remain unmarried. An Anglican, Lutheran, or Methodist bishop can be married. In the Orthodox Church, and in the Uniate Churches that are affiliated with Rome, only unmarried priests can become bishops, and bishops are not permitted to marry. See the entry on celibacy.
Bishops are the successors of apostles. For example, the Bishop of Rome is the successor-in-office of the Apostle Peter, and the Bishop of Alexandria is the successor-in-office of the Apostle Mark (one of the Seventy).
When they are ordained, Methodist ministers are presented with a document showing their apostolic succession back to Peter, but they are not priests in the Anglican Communion, since their ordinations pass through Wesley, who was never a bishop.
Duties and Authority of Bishops
Like apostles, bishops are missionaries who have the authority to establish churches, to appoint bishops to supervise them, and to ordain priests to run them. Saint Patrick became a bishop in order to evangelize Ireland. Alaska was originally evangelized by St. Herman of Alaska, a Russian Orthodox bishop.
Unlike apostles, they cannot single-handedly appoint a priest to the office of bishop. It took (and still takes) three bishops working together to do that, just as it takes three rabbis to ordain a rabbi. They also cannot work miracles at their own discretion (Acts 3:6) as the apostles could. Bishops also have the ability to appoint local feast and fast days for the churches under their supervision.
Since a bishop had authority over the churches he founded, it sometimes happened that a church came under the authority of a different bishop than the church next door, and that led to unseemly arguments among Christians. There was also the problem of priests, both real and fake, unilaterally moving from one bishop to another. Canon 2 of the Second Ecumenical Council held in Constantinople in 381, solved these problems by setting up geographical boundaries and prohibited overlapping jurisdictions.