The Proskomedia or the Liturgy of Preparation, which is performed before the beginning of the Divine Liturgy, captures the essence of the Liturgy.  At the preparation table on the side of the sanctuary, the priest cuts the prosphora (the bread) according to the strictly prescribed manner. 

The prosphora is cut into four parts: one for Christ himself (a cube), another for Mary the Mother of God (a pyramid), another for the Nine ranks (prophets and the forerunners such as St. John the Baptist, Moses, Aaron, Elijah, Elisha, King David, Jesse, prophet Daniel, and Daniel’s three holy youths), and the last part for the Church Fathers, government leaders, the church founders, and the congregation (the living and the dead).  See the diagram below. Thus, in the sacrifice of Christ, being offered to God as the Gift; the faithful (the living and the dead) are joined alongside with Him and with all the Saints and the Forerunners to be offered and consecrated as “the living sacrifice to God, holy and acceptable” (Rom. 12:1).

The square seal of Christ with the imprint ΙΣΧΣ, referring to Ιησούς Χριστός (Jesus Christ) and ΝΙΚΑ (νίκα) “victory” is baked into the center of the prosphora, which is cut into a cube along the edges of the seal, as described above, before it is place on the discos, as the priest prays:

Like a lamb that is led to the slaughter…Like a sheep that is silent before its shearers, he does not open his mouth...The Lamb of God that takes away the sin of the world is sacrificed for the life and the salvation of the world (The Divine and Holy Liturgy, (Grass Lake, Michigan: Romanian Orthodox Episcopate of America, 2005), 19-20). 

Having placed the square seal particle on the discos, the priest then pierces on the side of it that is marked ΙΣ (the right side of the seal, the first and the last letters of Ἰησοῦς Χριστός (IS) capitalized in Greek ("ΙΗΣΟΥΣ ΧΡΙΣΤΟΣ"), and says:

One of the soldiers pierced his side with a lance (Id., 20).  

(Later during the Anaphora, prior to the Communion, the square seal representing Christ, ΙΣΧΣ and ΝΙΚΑ (the cube) is cut into four parts, each containing two letters—just as in ancient Jerusalem the animal is cut into parts to be offered as the sacrifice during the burnt offering.)

The priest then pours wine and warm water into the chalice, saying:

 And immediately there came out blood and water… (Id., 20).  

The priest then cuts the triangular portion of Mary from the prosphora (the right side of the seal of ‘Jesus Christ Conquers’) and places it on the discos, saying:

In honor and memory of our most blessed, glorious Lady, the Birthgiver of God and Ever-Virgin Mary, through whose intercessions, O Lord, accept this sacrifice on your heavenly altar (Id., 21).  

The priest then cuts the third group of nine particles from the prosphora—representing the heavenly hosts including Michael and Gabriel, the Prophets (Moses and Aaron, Elijah and Elisha, etc.), the Forerunners (David and Jesse, the three holy youths of prophet Daniel, etc.), John the Baptist, the 12 and the 70 apostles, the great teachers and fathers of the Church —and places it on the discos.  As he prepares the last group, the priest remembers (in prayer) the hierarchs, the local church founders, and most importantly the member of the congregation (both the living and the dead) by reading the names written on the diptychs (which he will read again during the Divine Liturgy after the consecration of the Gifts during the Anaphora segment).  

On the discos, the whole Church is represented along with the Body of Christ: the prophets, the forerunners, the apostles, the hierarchs, the church founders and the members (the living and the dead). They are all incorporated into one Body of Christ and are offered as the Gift of sacrifice to God. Thus the Ruthenian Recension text has the title of the Liturgy correct: “The Divine Liturgy of Our Father Among the Saints.” Reading the title literally, the Liturgy is a sacrificial rite performed by God the Father in the present of all the Saints offering his Son (as Abraham did) as the Lamb of God slaughtered for the redemption of the world. On the discos is represented the Kingdom of God, whose King wears the purple roke of mockery and the crown of thorns hanging from the Cross. Humility is at the heart of His throne.

Once the particles are placed on the discos, the priest puts the star (supported by four legs) above the particles and covers over both the chalice and the discos with cloth or aer, representing Christ’s swaddling cloth at his birth below the star of Bethlehem and at His burial in the tomb.  The whole liturgy is a concrete presentation of Christ’s life from birth to death, and the proclamation of his Incarnation, Resurrection, and Ascension.  Moreover, the particles cut from the prosphora and the wine represent the whole creation as they are offered to God as the sacrificial Gifts, like Christ Himself, to be lifted up during Anaphora (“offering up”):

For You are the Offerer [προσφέρων] and the Offered [προσφερόμενος]; the Accepted [προσδεχόμενος] and the Distributed [διαδιδόμενος, ‘the given’]”)

The Divine Liturgy of St. John Chrysostom, (Copyrighted in 2004 by Rev. Jon Magoulias), 14.

Christ reveals himself as the Gift that gives itself by abandoning itself without remainder in humility (kenosis).  All the visible Elements must be completely consumed (by the deacon or the priest) without leftover afer the Liturgy is completed.  The Gift is given, received, and offered (to us and to God) all at once completely (without leftover). The Eucharist makes happen (by the work of the Holy Spirit) Christ’s Incarnation that includes His birth, death, resurrection. He “condescends” (Chrysostom) and “became flesh” (John 1:14) by emptying himself to the point of death (Phil. 2:7) in order to assume humanity so as to lift it up back to God:

Blessed is He that comes in the name of the Lord.  God is the Lord and has revealed himself to us! [sings the choir as the Communion begins.] 

The Syro-Chaldean desert Saint, Narsai of Nisibi speaks of the glory of the coming of the Lord in the Great Entrance of the Liturgy that culminates in the Eucharist as follows:

The Holy One comes forth on the plate and in the cup, in glory and majesty, accompanied by the presbyters and deacons, in grand procession. Millions of angels and servants of the fire of the Spirit go before the Body of Our Lord, glorifying him. All the people and all the sons of the Church rejoice when they see the Body come from the alter.

(Explanation of the Mysteries of the Church, attributed to Narsai Of Nisibi, as quoted in Instruction For Applying the Liturgical Prescriptions of the code of Canon of the Eastern Churches, a reproduction of the official English translation, Congregation for the Eastern Churches, (The Vatican: Libreria Editrice Vaticana, 1996), 56).

Finally, the Gift is given in the form of nourishment, as the heavenly bread and the wine, like the heavenly manna that sustained the Israelites in the desert.  Likewise, the Gifts of the Eucharist sustain the faithful on daily basis: “Give us this day our daily bread…”  The heavenly bread sustains us, as it sustains the whole Creation.  The Eucharistic Gifts are then the Gifts of recapitulation: the whole Creation is nourished by the blood of Christ, the ultimate Gift of sacrifice. Sacrifice is the ultimate giving, giving to the end. It is the inexhaustible giving. What is blessing but a pure giving without end and without return? Sacrifice thus redeems being. The kenotic Gift or the Gift of sacrifice sanctifies being (represented by the bread and the wine), so that being in turn can be offered back to the Creator as the gift.  Here the logic of the sacrifice (i.e., the giving of the Gift to the end) supercedes the logic of exchange (in which being thrives); because it gives to the end, to the point of incurring irrecuperable deficit, which is precisely what the ancient Greek term “liturgy” means (λειτουργία - “a public service” (Liddell and Scott, Greek-English Lexicon) or, as Levinas puts it, “a putting out of funds at a loss” (1986: 350)). Liturgy is a service rendered in sacrifice. Christ’s life as a whole, his kenotic sacrifice (i.e., his descent, Incarnation, and death—all combined (Phil. 2:5-8)) was a liturgy, a work of sacrifice to the point of complete emptiness. Such was Christ’s Gift—a gift given without end, like blessing.

Your only Son… has redeemed me with his blood. Let not the proud disparage me, for I am mindful of [the price paid for me]. I eat it, I drink it, I dispense it to others, and as a poor man I long to be filled with it among those who are fed and feasted. And then do those who seek him praise the Lord.

(Augustine, Confessions, X, xliv, 70; Maria Boulding’s translation altered, per John C. Cavadini (2010: 96)).

The liturgical context of the Eucharist is clear in these lines written by the Bishop of Hippo.

See also Proskomedia in Orthodox Wiki.

The Text of the Proskomedia

  

 
The portions of the prosphora arranged on the discos during the Proskomedia before they are further cut and mixed with wine and water in the chalice during Anaphora before the Communion toward the end of the Liturgy.

The portions of the prosphora arranged on the discos during the Proskomedia before they are further cut and mixed with wine and water in the chalice during Anaphora before the Communion toward the end of the Liturgy.