Christianity first spread in the predominantly Greek-speaking eastern half of the Roman Empire. The Apostles traveled extensively throughout the empire, establishing communities in major cities and regions, with the first community appearing in Jerusalem, followed by communities in Antioch, Ethiopia and others. Early growth also occurred in the two political centers of Rome and Greece, as well as in Byzantium (initially a minor centre under the Metropolitan of Heraclea, but which later became Constantinople). Orthodoxy believes in the apostolic succession that they believe was established by the Apostles in the New Testament; this played a key role in the communities' view of itself as the preserver of the original Christian tradition. Historically the word "church" did not mean a building or housing structure (for which Greek-speakers might have used the word "basilica") but meant a community or gathering of like peoples (see ekklesia). The earliest Ecclesiology would posit that the Eucharistic assembly, under the authority and permission of a Bishop, is what constitutes a Church. As St. Ignatius of Antioch said, "Let no man do anything connected with the Church without the bishop. Let that be deemed a proper Eucharist, which is [administered] either by the bishop, or by one to whom he has entrusted it. Wherever the bishop shall appear, there let the multitude [of the people] also be; even as, wherever Jesus Christ is, there is the Catholic Church. It is not lawful without the bishop either to baptize or to celebrate a love-feast."
The original church or community of the East before the Great Schism comprised:
The church of Rome by tradition was founded by both Saint Peter and Saint Paul.
Systematic persecution of the early Christian church caused it to become an underground movement. The first above-ground legal churches were built in Armenia (see Echmiadzin). Armenia became the first country to legalize Christianity (around 301 AD) under King Tiridates III and also embrace it as the state religion in 310 AD. However, illegal churches before "Christian legalization" are mentioned throughout church history; for example, in the City of Nisibis during the persecutions of Diocletian. Of the underground churches that existed before legalization, some are recorded to have existed in the catacombs of Europe i.e. Catacombs of Rome and also in Greece (see Cave of the Apocalypse, The Church of St George and the church at Pergamon) and also in the underground cities of Anatolia such as Derinkuyu Underground City (also see Cave monastery and Bab Kisan). Also noteworthy are the Church of St Peter in Antioch and the Cenacle in Jerusalem.
Much of the official organizing of the ecclesiastical structure, clarifying true from false teachings was done by the bishops of the church. Their works are referred to as Patristics. This tradition of clarification can be seen as established in the saints of the Orthodox Church referred to as the Apostolic Fathers, bishops themselves established by apostolic succession. This also continued into the age when the practice of the religion of Christianity became legal (see the Ecumenical Councils).
The Biblical canon began with the officially accepted books of the Koine Greek Old Testament (which predates Christianity). This canon, called the Septuagint or seventy, continues to be the Old Testament of the Orthodox faith, along with the New Testament's Good news (gospels), Revelations and Letters of the Apostles (including Acts of the Apostles and the Epistle to the Hebrews). The earliest text of the New Testament was written in common or Koine Greek. The texts of the Old Testament had previously been translated into a single language, Koine Greek, in the time of Ptolemy II Philadelphus in 200 BC.
The early Christians had no way to have a copy of the works that later became the canon and other church works accepted but not canonized. Much of the original church liturgical services functioned as a means of learning these works. Orthodox Church services today continue to serve this educational function. The issue of collecting the various works of the eastern churches and compiling them into a canon, each being confirmed as authentic text was a long protracted process. Much of this process was motivated by a need to address various heresies. In many instances, heretical groups had themselves begun compiling and disseminating text that they used to validate their positions, positions that were not consistent with the text, history and traditions of the Orthodox faith.
Liturgical services, especially the Eucharist service, are based on repeating the actions of Jesus ("do this in remembrance of me"), using the bread and wine, and saying his words (known as the words of the institution). The church has the rest of the liturgical ritual being rooted in Jewish Passover, Siddur, Seder, and synagogue services, including the singing of hymns (especially the Psalms) and reading from the Scriptures (Old and New Testament). The final uniformity of liturgical services became solidified after the church established a Biblical canon, being based on the Apostolic Constitutions and Clementine literature.
In the Orthodox view, the Bible represents those texts approved by the church for the purpose of conveying the most important parts of what it already believed. The oldest list of books for the canon is the Muratorian fragment dating to c. 170 (see also Chester Beatty Papyri). The oldest complete canon of the Christian Bible was found at Saint Catherine's Monastery (see Codex Sinaiticus) and later sold to the British by the Soviets in 1933. Parts of the codex are still considered stolen by the Monastery even today. These texts (as a whole) were not universally considered canonical until the church reviewed, edited, accepted and ratified them in 368 AD (also see the Soteriology from the Orthodox perspective is achieved not by knowledge of scripture but by being a member of the church or community and cultivating phronema and theosis through participation in the church or community.