It's Greek, they're Greek Orthodox.
The basic form of Christian worship has remained more-or-less the same since the time of Jesus' first disciples. We call it the liturgy, the word "liturgy" comes from the Greek word leitourgia, literally translated as "work of the people" or "public work"; it refers to what happens when God's people come together for worship, it is the corporate, gathered-together worship activity of the Church. Such worship, just like the ancient Israelites and the Jews in Jesus' time, structured their worship in such a way as to bring together prayer, song, the reading of God's word, and basic instruction in faith.
Many of the earliest Christians, being Jews, continued to worship every Sabbath at their local synagogue, the following morning on the first day of the week they would come together for more prayer and to share in the Eucharist, Christ's Supper of bread and wine which He commanded that we receive together; where He offers us His flesh and blood, "This is My body broken for you" is what He said. As non-Jews began to convert to Christianity, and as the synagogue became an increasingly more hostile place for Jewish Christians, both Jewish and Gentile Christians simply came together in the larger homes of Church members (often wealthy women, such as St. Phoebe the Deacon mentioned in Romans 16:1-2). There in these "house churches", the structure of the synagogue worship continued, though in a distinctively Christian way, as well as the Lord's Supper. These two parts of Christian worship, the "Liturgy of the Word" based off of the old synagogue pattern of worship, and the "Liturgy of the Altar", influenced by the pattern of worship of ancient Israel in the Tabernacle/Temple focused on the Lord's Supper became the full Christian Liturgy, dividing these two halves of the service was "The Peace", following the biblical commandment for Christians to "greet one another with a holy kiss"--a kiss on the cheek was a sign of peace and friendship in the ancient world (the modern equivalent would be a handshake or a hug).
That pattern of worship has continued from the days of the New Testament until now. Hence you will find that the way Catholics, Orthodox, and traditional Protestants worship is all exceedingly similar. Because we are still using the same worship blueprint that Jesus and His Apostles used. And if you pay close attention, even in less traditional Protestant churches (Baptists, Pentecostals, non-denominational churches), some of this very basic structure is still used, if more loosely.
There's a reason why it has endured for thousands of years: it's biblical, it's faithful, it saturates us with the word of God.
-CryptoLutheran