The central worship service of the Orthodox Church, celebrating the Eucharist (Holy Communion). Usually celebrated on Sundays and feast days, the Divine Liturgy consists of the Liturgy of the Word (scripture readings) and Liturgy of the Faithful (Eucharistic prayer and communion). The most common forms are the Liturgies of St. John Chrysostom and St. Basil the Great.

The birth of St. John the Baptist, the Forerunner of Christ, to the elderly Zacharias and Elizabeth. Celebrated on June 24th, this feast honors the one who prepared the way for Christ's ministry. John's birth was miraculous, and he grew up in the desert to become the voice crying in the wilderness, baptizing Christ in the Jordan.

The joint commemoration of the two great apostles: Peter, the leader of the Twelve, and Paul, the Apostle to the Gentiles. Celebrated on June 29th after the Apostles' Fast, this feast honors both their ministries and their martyrdom in Rome. Though different in background, both were instrumental in establishing the early Church.

The brother physicians who provided free medical care and were martyred under Diocletian. Celebrated on November 1st, these 'Unmercenary Healers' treated both physical and spiritual ailments without accepting payment. They are patron saints of physicians and pharmacists. Their example shows how professional skills can be a form of Christian ministry and service.