When the Church, literally the assembly of people who are called together, assembles as God’s People to worship, this gathering is called the liturgy of the Church. The word liturgy means the work of the people. Thus the Divine Liturgy of the Christian Church means the common work of God done by the people of God.
Eastern Orthodox services trace their beginnings back to the Old Testament liturgical rites and services of the Hebrews. They are a treasury of Scripture readings, prayers, hymns, and canons composed by the Saints and pious Christians throughout the ages. Like our Jewish predecessors, Orthodox services are liturgical, sacramental, and ceremonial. Many of the hymns you hear come from the Psalms. Most of them are sung or chanted, as has been the tradition since the days of Jewish/Christian practice. In the New Testament Church the liturgy is centered in the person of Jesus Christ. The Christian Church retains the liturgical life of the Old Testament in a new and eternal perspective. Thus, the prayers of the Old Testament, the scriptures and the psalms, are read and sung in the light of Christ. The sacrifice of the Body and Blood of Christ replaces the Old Testament sacrifices in the temple. And the Lord’s Day, Sunday, replaces the old Jewish sabbath which is Saturday. Some of the ancient document sources of the Orthodox liturgical order of service go back to the second (Justin Martyr, c. A.D. 150) and third centuries (Hippolytus, c. 215 A.D.). Eastern liturgies went through development in the fourth and fifth centuries. They became stabilized in the sixth century, and by the eighth century were so fixed that they have hardly changed even to today.
What is the content of Orthodox liturgical worship?
One of the striking characteristics of Orthodox worship is its near total integration with its theology. It is this blending of theology and worship that gives Orthodoxy its thoroughly liturgical character. From the Orthodox Christian perspective, Western Christianity exhibits a breach or rupture between theology and liturgical experience. In Orthodox Christianity they are a single, inseparable act. Participate in the liturgical cycle of the Orthodox Church and you will hear and see its theology, through its text, chant, hymnography and iconography.