Orthodox Christianity grew out the churches established by the missionary Paul in the countries surrounding the Mediterranean Sea. During this time, much of the Mediterranean region was under Roman control. The Roman empire split into a Western and Byzantine empires in 395 CE. This political separation allowed Christianity to develop along separate lines, with different traditions and liturgy. The Western empire collapsed in 476 CE although the papacy continued in Rome. The relationship between the Western and Eastern churches gradually declined, particularly when the Franks gained sufficient influence with the papacy to cause their king to be crowned Holy Roman Emperor in 800 CE. This action was taken as a snub to the Eastern emperor and the Byzantine empire. Political and theological differences finally resulted in the East–West Schism which separated the empires and churches in 1054 CE. The Western church, lead by the Pope in Rome, became the Catholic Church. The Eastern church became known as the Orthodox Church and was generally located in the Eastern Mediterranean.
Comparison with Catholicism
Because of their shared history and origins, the Catholic and Orthodox churches have significant similarities and are in sharp contrast with later Protestant denominations. Various attempts to reunited the Catholic and Orthodox churches failed. The two churches remain separate to this day with no inter-communion existing between them. Like Catholicism, Orthodox Christianity claims to be the actual church established by Christ through missionaries like Paul. Both churches also believe that the lineage of churches establishes its authority. Both churches have liturgical services conducted by members of the clergy. In both, the clergy wear vestments and often using incense burning in a censer
Orthodox Churches do not defer to a central conference, headquarters or a particular leader. They are, instead, self-governing bodies, usually national churches that operate as a federation. Unlike Catholicism, Orthodox Christianity does not have a scholastic tradition (theology largely influenced by Aristotelian thought). Orthodox churches are known for their mysticism,  adherence to tradition, as well as veneration of icons and relics. Many other differences in emphasis and doctrine exist. 
Services are liturgical, often with a mixture of Greek and the local language. There is only one Eucharistic service on Sunday and is preceded by several shorter services. The service is largely sung without instruments while mostly standing. The usual liturgy is the Divine Service by St. John Chrysostom although many longer liturgies are sometimes used.