The icon has the Apostles sitting, as on Mount Sion, representing the first Church community, the beginning of the Christian Church. They form a semicircle to express the unity of the Church, the Mystical Body of Christ. The icon is not a depiction of the historical events of Pentecost, but it signifies that this is a great event for all time.
As with many icons, the Apostles are pictured in an inverse perspective, the figures grow larger as they recede into the background. Also, the building that the Apostles were in, is shown as background.
The Holy Spirit
At the top of the icon is another semicircle, with rays coming from it. The rays are pointing toward the Apostles, and the "tongues of fire" are seen descending upon each one of them signifying the descent of the Holy Spirit.
At the center of the group of Apostles, there is a place which is unoccupied. It is reserved for Christ, the invisible head of the Church. Some ancient icons symbolize Christ's invisible presence with an altar, the throne of His glory. Clearly, no one else can be depicted here.
The group of twelve represent the Church, not just those mentioned in the book of Acts as being with the others on the day of Pentecost. Pictured in the icon is Paul, who became an Apostle of the Church and the greatest missionary. The four Evangelists, Matthew, Mark, Luke, and John, are shown holding the not yet written books of the Gospel. Other Apostles are holding scrolls that represent the teaching authority given to them by Christ.
In yet another semicircle, at the bottom of the icon, is a symbolic figure of a king. He is in a dark place that represents the world enveloped by sin. This one person represents the whole world that had formerly been without the light of faith. He is bent over to show he was made old by the sin of Adam. Through the power of the Holy Spirit the Church brings light to the whole world by her teaching. Sometimes, the figure is shown coming out, into the light, having a cloth containing scrolls which represent the teaching of the Apostles.