In Orthodox usage, liturgy means common work or common action. The Church gathers as the people of God to pray, hear the Word, offer thanksgiving, and receive Christ in the Holy Eucharist. Because of this, the Divine Liturgy stands at the center of Orthodox Christian life.
Two main movements
The Liturgy is often described in two broad movements: the Liturgy of the Word and the Liturgy of the Faithful. The first is centered on psalms, hymns, apostolic readings, and the Gospel. The second is centered on the Eucharistic offering, thanksgiving, and communion.
Sunday and the Resurrection
The Divine Liturgy is especially associated with Sunday, the Lord's Day, the day of Christ's Resurrection. It is also celebrated on many feast days and, in monasteries and some parishes, more frequently according to local practice.
Communion and preparation
Holy Communion is the sacramental participation in the Body and Blood of Christ. In Orthodox practice, reception of Communion belongs to Orthodox Christians who are living the life of the Church and preparing according to the guidance of their priest and local tradition.
What a visitor can do
Visitors are normally welcome to attend and observe. A first visit is best approached with humility: stand where you are comfortable, listen, follow the parish's lead, and ask questions afterward rather than trying to understand everything at once.
Practices around preparation, confession, fasting, and receiving Communion can vary by parish and jurisdiction. Speak with the local priest for concrete guidance.