As excerpted from the Greek Orthodox Church website.

In the icon of the Feast of the Transfiguration, Christ is the central figure, appearing in a dominant position within a circular mandorla. He is clearly at the visual and theological center of the icon. His right hand is raised in blessing, and his left hand contains a scroll. The mandorla with its brilliant colors of white, gold, and blue represent the divine glory and light. The halo around the head of Christ is inscribed with the Greek words O on, meaning "The One Who is."

Elijah and Moses stand at the top of separate mountain peaks to the left and right of Christ (Elijah stands on the left side in the icon and Moses, holding the Ten Commandments, stands on the right side). They are bowing toward Christ with their right hands raised in a gesture of intercession towards Him. Saint John Chrysostom explains the presence of these two fathers of the faith from the Old Testament in three ways. He states that they represent the Law and the Prophets (Moses received the Law from God, and Elijah was a great prophet); they both experienced visions of God (Moses on Mount Sinai and Elijah on Mount Carmel); and they represent the living and the dead (Elijah, the living, because he was taken up into heaven by a chariot of fire, and Moses, the dead, because he did experience death).

Below Christ are the three Apostles, who by their posture in the icon show their response to the transfiguration of Christ. James (right) has fallen over backward with his hands over his eyes. John in the center has fallen prostrate. Peter (left) is kneeling and raises his right hand toward Christ in a gesture expressing his desire to build the three booths. The garments of the Apostles are in a state of disarray to indicate the dramatic impact the vision has had on them.

The icon of the feast directs our attention toward the event of the Transfiguration and specifically to the glory of God as revealed in Christ. This event came at a critical point in the ministry of our Lord, just as He was setting out on His journey to Jerusalem. He would soon experience the humiliation, suffering, and death of the Cross. However, the glorious light of the Resurrection was revealed to strengthen His disciples for the trials that they would soon experience.

The feast also points to the great and glorious Second Coming of our Lord and the fulfillment of the Kingdom of God when all of creation will be transfigured and filled with light.