It is the day before Easter and the last day of Holy Week, in which Christians prepare for Easter.
This day commemorates the day that Jesus Christ's body lay in the tomb.
Western Observation
In Roman Catholic Churches, the sanctuary remains stripped completely bare (following the Mass on Maundy Thursday) while the administration of the sacraments is severely limited. Holy Communion Is given only as Viaticum to the dying. All Masses are strictly prohibited. No Mass at all appears in the liturgy for this day. Many of the churches of the Anglican Communion as well as Lutheran, Methodist, and some other Churches observe most of the same; however, their altars may be covered in black instead of being stripped.
In some Anglican churches, including the Episcopal Church in the United States, provision is made for a simple Liturgy of the Word on this day, with readings commemorating the burial of Christ, but no Eucharist.
Liturgically speaking, Holy Saturday lasts until dusk, after which the Easter Vigil is celebrated, marking the official start of the Easter season. In Roman Catholic observance, during the "Gloria" of the Mass (which is the first Mass since that of Holy Thursday), the church statues and icons, in places where they are covered with purple veils during Passiontide, are dramatically unveiled.
Eastern Observation
In Eastern Orthodoxy this day, known as Holy and Great Saturday, is also called The Great Sabbath since it is on this day that Christ "rested" physically in the tomb. But it is also believed that it was on this day he performed in spirit the Harrowing of Hades and raised up to Paradise those who had been held captive there.
Matins of Holy and Great Saturday (usually held on Friday evening so more people can attend) takes the form of a funeral service for Christ. The entire service takes place around the Epitaphios (Slavonic: Plashchanitza), an icon in the form of a cloth embroidered with the image of Christ being prepared for burial. The first part of the service consists of chanting Psalm 118 (the longest psalm in the Bible) with hymns (enkomia) interspersed between the psalm verses. The predominant theme of the service is not so much one of mourning, but of watchful expectation:[1]
Today Thou dost keep holy the seventh day,
Which Thou has blessed of old by resting from Thy works.
Thou bringest all things into being and Thou makest all things new,
Observing the Sabbath rest, my Saviour, and restoring strength.[2]
Near the end of Matins, following the Lauds at the end of the Great Doxology, the Epitaphios is taken up and carried in procession around the outside of the church, while all sing the Trisagion, exactly as is done in an Orthodox funeral service.
On Saturday morning, a vesperal Divine Liturgy of St. Basil the Great, is celebrated. This is the longest Divine Liturgy of the entire year and, traditionally, the latest. After the Little Entrance there are 15 Old Testament readings which recall the history of salvation. Just before the Gospel reading (Matthew 28:1-20) the hangings, altar cloths, and vestments are changed from black to white and the deacon performs a censing of the church. In the Greek tradition the clergy strew laurel leaves and flower petals all over the church to symbolize the shattered gates and broken chains of hell and Jesus' victory over death. While the liturgical atmosphere changes from sorrow to joy at this service, the Paschal greeting, "Christ is risen!" is not exchanged until after the Paschal Vigil later that night, and the faithful continue to fast. The reason for this is that the Divine Liturgy on Holy and Great Saturday represents the proclamation of Jesus' victory over death to those in Hades, but the Resurrection has not yet been announced to those on earth (this will take place during the Paschal Vigil).
Great Lent was originally the period of catechesis for new converts in order to prepare them for baptism and chrismation on Pascha (Easter). Prior to the composition of the current Paschal Vigil of St. John of Damascus[3] this day's vesperal Liturgy was the main Easter celebration, and the traditional time to receive converts is still after the Vesperal Divine Liturgy.
Later that night (around 11:00 pm), the Paschal Vigil begins with the Midnight Office, during which the Canon of Holy Saturday is repeated. Then, all of the candles and lights in the church are extinguished, and all wait in darkness and silence for the proclamation of the Resurrection of Christ.