Picture from the Orthodox Wiki entry on Passion Week:
A worshiper prostrates before the cross at the Twelve Passion Gospels service at St. Mary Orthodox Church in Cambridge, Massachusetts.
Great and Holy Week, also called Holy Week or Passion Week, begins at sundown on Lazarus Saturday, the day before Palm Sunday, and continues until Pascha. For Eastern Christendom, it is the most sacred part of the liturgical year, as Pascha, not the Nativity as it is in the West, is the greatest Feast of the Church Calendar. During Holy Week, Orthodox services are both at their most muted, and their most moving, not to mention most frequent. If a parish did everything available, the church wouldn’t be empty at any point all week (that’s only a slight exaggeration). Our parish is not large, but I estimate that we will be anywhere from 25 – 30 hours in church, not counting the baptisms and chrismations on Great and Holy Saturday or Pascha services.
Note: Western Christians may be a bit disoriented by when we celebrate the days of Holy Week. Following ancient Judaic tradition, we reckon the days throughout the year from sunset to sunset, excepting only Pascha, which begins at midnight, and in some parishes in the United States due to Western influence, Nativity (also, in those parishes, at midnight). So on the evening of Great and Holy Wednesday, we celebrate Great and Holy Thursday services, and so forth.
During Great and Holy Week, we reverse the order of services to mark the deep state of distress of the world. Matins are celebrated in the evenings, and Vespers in the mornings. The Matins services are known as Bridegroom Matins, because the theme is the Parable of the Ten Virgins, and the Second Coming, reminding us that Pascha is not merely a historical celebration, but a preparation for when He comes again. Also, a censer without bells is used to mute our celebration of the Passion of Christ.
On Great and Holy Wednesday, it is Byzantine custom to offer the Liturgy of Holy Unction, when we are annointed and healed. Many parishes in the Slavic tradition have adopted Holy Unction as a regular service during Great and Holy Week. Wednesday is also the day on which Judas agreed to betray Christ with a kiss for thirty pieces of silver, which we mourn throughout the year with prayer and fasting. In many parishes, the Homily of St Leo the Great on the Passion of Christ is read.
On Great and Holy Thursday morning, we commemorate the Last Supper with Great Vespers followed by the Divine Liturgy of St Basil the Great with the Reserved Eucharist. In cathedrals, or parishes with a visiting bishop, the bishop washes the feet of 12 priests and deacons after the Divine Liturgy in the morning.
In the evening, we have the Great and Holy Friday Matins, with the reading of the Twelve Passion Gospels. This is the closest equivalent in Orthodoxy to the Stations of the Cross.
After the Fifth (or perhaps the Sixth) Gospel, the priest nails Christ to the cross and we prostrate ourselves before it (see picture at the top of the page).
On Great and Holy Friday morning, the 1st, 3rd, 6th, and 9th Hours are celebrated back to back, and are known as the Royal Hours. The Royal Hours culminates in Great Vespers, when the priest takes Christ down from the cross, wraps the body in white linen, and lays the body upon the altar. In the evening are the Lamentations, the Church’s funeral service for Our Lord, when we lay him in the sepulchre, then process with lighted candles to commemorate Christ’s descent into Hades. Of all of the Church’s services, Great and Holy Friday is arguably the most moving, regularly bringing grown men to tears.
On Great and Holy Saturday morning, we celebrate Great Vespers and the Divine Liturgy of St Basil the Great, and commemorate Christ’s descent into Hades and trampling down death by death. We sing “Arise, O Christ!” in anticipation of Pascha.
In the afternoon, are baptisms and chrismations (for cathechumens), an ancient tradition.
Let God Arise!
Pascha, or the Feast of Feasts, is the most important Feast in Eastern Christendom, and begins late on Saturday evening in a darkened church with the Resurrection Vespers, when the Odes of Lamentation are sung. The priest lights a candle from the altar vigil lamp, and with it, lights our candles as he chants, “Come receive the Light from the Light that is never overtaken by night and glorify Christ who is Risen from the dead.” We then process around the outside of the church three times, and as the priest approaches the door, he leads us in singing the most joyful and triumphant hymn in Eastern Christendom, the Resurrection Hymn: “Christ has risen from the dead, trampling down Death by death, and bestowing life upon those in the tombs!”
We re-enter the now-lit church, and celebrate Pascha Matins and the Divine Liturgy, then eat an agape meal to break our fast. In the afternoon, we re-gather with our candles, greeting each other with “Christ is risen! Indeed, He is risen!” and celebrate the Agape Vespers.
The priest chants “Come receive the light” as deacons, servers, and parishioners light their candles from his, from St Nicholas Orthodox Church in Seoul, South Korea (yes, there’s an organ — ignore it):