Christianity began in the land of Palestine, primarily in Galilee and Judea. After Jesus' death and resurrection, the center of the church was Jerusalem, where the church actually met in the Temple. Most Christians at this time were Jews by birth.
The early success of the Christians in making converts led to persecutions by the priests and other Jewish officials, often driving them to cities outside Palestine to wait out the troubles. In these cities, such as Alexandria in Egypt and Antioch in Syria, the Christians continued to make converts. This began the movement of Christianity from Judaism into the Greek world. Within the first couple decades of its establishment, the early church also sent out missionaries throughout the Mediterranean World. The missionary Paul traveled in Asia Minor (modern-day Turkey), Greece, and even reached Rome. Other missionaries went west to Rome and Spain, east into Mesopotamia and ultimately even as far as India. With the destruction of Jerusalem and the Temple in 70, the Christians, along with the other Jews, were driven out of Jerusalem and lost this city as a center for over a century.
As the Church spread, the lines of communication between cities and the churches in them grew quite weak. Persecutions in the second and third centuries made any sort of widespread organization nearly impossible. So in smaller towns, each church was essentially in charge of itself, while in cities, there organization got beyond the city walls. Thus, across the empire, many different theological ideas were developed and many different modes of worship.
With the triumph of Constantine in 312 and then in 324, the Roman Empire began its transformation into the Holy Roman Empire--the Empire of the Christians. By 380, Christianity was made the Empire's sole legitimate religion, all others were officially "outlawed" (although it would take a couple of centuries to see this happen unofficially). Now unified and approved, Christianity began to transform itself into an organized religion. One key method for accomplishing this was the holding of Church Councils that made official decisions about correct doctrine and belief. (For a general discussion of Church Councils, go here.) The first council, the Council of Nicea in 325, banned Arianism, and later councils took their lead from that. The free-wheeling variability of the early centuries was replaced by central decisions concerning truth, supposedly enforced by the Emperor himself.
By 410, another problem appeared: Barbarians from the North! First the Visigoths sacked Rome in 410, and then the Vandals in 455, after taking control of Spain and Africa. Suddenly the strategic division of the Empire into the Latin West and the Greek East was developing into two separate empires. The Western Church, under the leadership of the Bishop of Rome, accomodated the invaders in ways that would ensure the survival of Christianity, but which lead to continued friction with the Eastern Church. There were decades where the two churches (still officially one) did not communicate with each other, then the climate would improve and they would try to reestablish ties. The friction generated by this process ultimately lead to the two churches excommunicating each other in 1054. The Western Church has since been known as the Roman Catholic Church, while the Eastern Church has been called the Orthodox Church.
In the middle of this period, another major change often goes unmentioned, namely, the coming of Islam. In the first few centuries of the new Christian, Holy Roman Empire, it covered the "known world." Every country around the Mediterranean was Christian. But with the coming of Islam between 638 and 732, the southern half of the Mediterranean World was conquered by Islam. Most of the churches in those countries survived, but were much decimated and were under strict regulation by the Moslem authorities. In Syria, the Syrian Orthodox Church continued to exist, while in Egypt, the Coptic Church remained. South of the Mediterranean, the Ethiopian Orthodox Church thrived. However, they were cut off from the Christians in the northern countries, who essentially forgot they existed.
The Protestant Reformation caused another major change in the Christian world. In 1517, a questioning Catholic priest and theologian named Martin Luther nailed "95 Theses" (note: "theses" is the plural of "thesis") for debate on the door of the Cathedral. (To read the 95 Theses, go here. For a biography of Luther, go here.) The reaction to these questions ultimately caused him to leave the church and found a new form of Christianity called Lutheranism. It was widely adopted in Germany and northern Europe. Other reformers followed, such as John Calvin. (For a biography of Calvin, go here. For a description of Calvinism, go here.) John Knox took Calvin's "Presbyterianism" to Scotland, while England was reformed almost out of spite. King Henry VIII could not have a son with his wife, so he wanted a divorce so he could take another one. (For the juicy details, go here.) When Rome refused to grant it, he took over the church in his own country and created the Anglican Church. His successor, Elizabeth I (he never managed to have a son) furthered the break with Rome by adopting many of the doctrines, ideas, and practices of other reformers.
North America became a land of reform when it was initially settled by Puritans and then by Protestants of other types, many trying to escape persecution in Europe. By the 1900s, it was also a place of escape for many Catholics as well. Today, there are still more Protestants than Catholics in the United States, but Catholicism is the single largest church. And the protestant "ethic" of separation has led to the creation of hundreds of different protestant denominations in this country.
Orthodox Christianity is organized by what is essentially a continuation of the structure set up during the early days of the Holy Roman Empire. By 451, five Patriarchates had been established in the main cities of five key regions of the Empire: Constantinople for Asia Minor, Antioch for Syria, Jerusalem for Palestine, Alexandria for Egypt and North Africa and Rome for Italy and the West. Three of these were lost to the Moslem invasion. So after the split in 1054, only one Patriarchate remained, that of Constantinople. Over successive centuries, additional Patriarchates were created in Russia, Romania, Bulgaria, Serbia and Soviet Georgia. The Patriarchs are all considered equal, althought the Patriarch of Constantinople is the "equal among equals." He claims no power equivalent to the Roman Catholic Pope. There are also Orthodox Churches in Cyprus, Finland, Greece, Poland, and Czechoslovakia. The Orthodox Churches are often called "Greek Orthodox" because that is the language of their Bible and their liturgy.
The hierarchical system of the Orthodox Churches did not have the Patriarchs at their head, but instead each countriy had a council of Bishops. Indeed, while each region of local churches "gather around" its bishop. Underneath him are priests and deacons, who are responsible for the individual churches. Priests and deacons are generally married, but bishops cannot be. They are usually chosen by the council from the monastic clergy who have taken vows to remain celebate. The authority of the bishops comes from the laying on of hands, which is believed to go all the way back to the apostles.
Monasticism is important in Orthodoxy. Unlike Catholicism, there are no monastic orders. Each monastery is independent, with its own rule and traditions. Furthermore, Orthodoxy retains the tradition of independent monks, like the earliest desert monks of Egypt. Monks take vows of celibacy. For a brief essay about early monks, go here.
Most Orthodox Christians belong to the laity. They regularly attend Mass and the annual festivals. They are active participants in the veneration of saints through their icons. For January's saint calendar, go here.
The Roman Catholic Church claims to be the successor of St. Peter (one of the original 12 apostles) who founded the See of Rome. The Bishop of Rome claims to be his successor through an unbroken chain of laying-on-of-hands. The Bishop of Rome was one of the first three Patriarchs established by the Council of Nicea. From this position the Bishop began to establish the claim of superiority over the eastern bishops. When the Italy and the West was cut off by the barbarian invasions of Rome in the fifth century, the Bishop of Rome essentially became the leading authority, at time both civil and religious. Over the centuries, the Bishop of Rome took on the title, "le pap," (meaning "Father") which is translated into English as the "Pope." (For lots of information about the Pope, go here. Be sure to check out the page where St. Peter morphs into John Paul II! Here you can find the "Pope's own" web site in the Vatican.)
The Roman Catholic Church is thus defined as those Christians who recognize the Pope as the ultimate human religious leader and who deem that the See of Rome has supreme religious authority.
The Catholic Church is hierarchical. Each local church is attached to a district called a parish and it presided over by a priest. A group of parishes in a region are together called a diocese and are presided over by a bishop. Although traditionally the bishop's role is defined as that of a teacher and a leader of worship (in the Mass), in modern times he has become much more of a manager and administrator than a leader. The title Archbishop is usually given to a bishop who governs the largest or oldest diocese in a region of dioceses (this region is usually termed a province). Some bishops are chosen as Cardinals by the Pope. They become members of the College of Cardinals which is responsible for choosing a new pope when the current one dies.
The priest is both a liturgical leader, as the name implies, and a pastor. He is responsible for the administration of the sacraments, including Mass, as well as for looking after the members of his parish. The priest also serves as an intercessor who helps each individual mediate their relationship with God. They hear confessions, assign penance to help erase sins, and generally help people reach up to heaven.
In Catholicism, the laity has traditionally played a passive role. They have taken little part in church governance or in leading worship. Since Vatican II, this has changed significantly. Each parish church now has many lay committees which assist the priest in governing the church. The laity often design, lead, and conduct worship services, including--under a priest's supervision--the giving of the Eucharist.
Catholicism has also encouraged the development of "orders," groups of men and women who take vows of celibacy and who dedicate themselves to worshipping God and to helping their fellow Christians. These monks and nuns are essentially lay religious professionals, they do not necessarily take vows to become priests, but they dedicate themselves to full-time religious service. They usually live together in a monastery or a nunnery. They take vows of poverty, celibacy, and obedience. The latter means obedience to the rule of their order. (To read a copy of the Rule of St. Benedict, go here.) Traditionally, they would wear clothing that specifically indicated their order, but since Vatican II, many nuns and monks have worn "street" clothing. Some examples of religious orders are: The Society of Jesus (a.k.a. Jesuits), the Order of St. Benedict (a.k.a. the Benedictines), the Order of St. Francis (a.k.a the Franciscans), the Sisters of Mercy, and the Carmelite Sisters. For on-line information, go here.
The wide variety of protestant churches have adopted a wide variety of organizational structures. The Anglican churches, for example, have kept the hierarchy of bishops and are lead by the Archbishop of Canterbury and the King/Queen of England. The baptist churches, by contrast, have rejected not only the hierarchy but even the idea of priest. Instead they have minsters or pastors, rejecting the intercessory role claimed by the priest. In the United States, some baptist churches have joined in regional or national societies for administrative purposes. In these, the pastors are all equal, with no bishops or other higher ranks. An example of this would be the Southern Baptists, although their conventions are beginning to exercise theological control over member churches in a manner oddly similar to that of Orthodoxy.
In general, the Protestant Churches have also rejected the concept of lay orders and of monasticism.
Along with the reduction of hierarchy, Protestantism has increased the importance of the laity in both theological and administrative terms. In most Protestant demoninations, the laity exercise some control over the hiring and firing of their pastor. They determine church policy and advise the pastor on matters of non-theological concerns. They assist in leading worship and organize many of the activities of the church. In some denominations, the laity also participate in regional and national conferences, helping to set policy and sometimes even theology.
Protestantism has also lead the way in giving women the ability to become minsters and pastors. By now, in many of the denominations that have bishops, such as Methodist and Episcopalian (US Anglicans), women have even been appointed as bishops.
There are literally thousands of sites relating to Protestantism and Protestant Churches. For a short list, go here. (I will select some key sites early next week.)