Within the Catholic Church, Eastern Orthodox, Oriental Orthodox, Anglican, Old Catholic and Independent Catholic churches and in the Assyrian Church of the East, bishops claim apostolic succession, a direct historical lineage dating back to the original Twelve Apostles. Within these churches, bishops are seen as those who possess the full priesthood and can ordain clergy – including another bishop. Some Protestant churches including the Lutheran and Methodist churches have bishops serving similar functions as well, though not always understood to be within apostolic succession in the same way. One who has been ordained deacon, priest, and then bishop is understood to hold the fullness of the (ministerial) priesthood, given responsibility by Christ to govern, teach and sanctify the Body of Christ, members of the Faithful. Priests, deacons and lay ministers cooperate and assist their bishops in shepherding a flock.
The term epískopos (Greek: ἐπίσκοπος), meaning "overseer" in Greek, the early language of the Christian Church, was not from the earliest times clearly distinguished from the term presbýteros (literally: "elder" or "senior", origin of the modern English word priest), but the term was already clearly used in the sense of the order or office of bishop, distinct from that of presbyter in the writings attributed to Ignatius of Antioch  (died c. 110).
The earliest organization of the Church in Jerusalem was, according to most scholars, similar to that of Jewish synagogues, but it had a council or college of ordained presbyters (Greek: πρεσβύτεροι elders). In Acts 11:30 and Acts 15:22, we see a collegiate system of government in Jerusalem chaired by James the Just, according to tradition the first bishop of the city. In Acts 14:23, the Apostle Paul ordains presbyters in churches in Anatolia.
Often, the word presbyter was not yet distinguished from overseer (Greek: ἐπίσκοπος episkopos, later used exclusively to mean bishop), as in Acts 20:17, Titus 1:5–7 and Peter 5:1.[b][c] The earliest writings of the Apostolic Fathers, the Didache and the First Epistle of Clement, for example, show the church used two terms for local church offices—presbyters (seen by many as an interchangeable term with episcopos or overseer) and deacon.
In Timothy and Titus in the New Testament a more clearly defined episcopate can be seen. We are told that Paul had left Timothy in Ephesus and Titus in Crete to oversee the local church. Paul commands Titus to ordain presbyters/bishops and to exercise general oversight, telling him to "rebuke with all authority".
Early sources are unclear but various groups of Christian communities may have had the bishop surrounded by a group or college functioning as leaders of the local churches. Eventually the head or "monarchic" bishop came to rule more clearly, and all local churches would eventually follow the example of the other churches and structure themselves after the model of the others with the one bishop in clearer charge, though the role of the body of presbyters remained important.
Eventually, as Christendom grew, bishops no longer directly served individual congregations. Instead, the Metropolitan bishop (the bishop in a large city) appointed priests to minister each congregation, acting as the bishop's delegate.