“In Byzantine art, and later Eastern Orthodox art generally, the Deësis or Deisis (Greek: δέησις, “prayer” or “supplication”), is a traditional iconic representation of Christ in Majesty or Christ Pantocrator: enthroned, carrying a book, and flanked by the Virgin Mary and St. John the Baptist, and sometimes other saints and angels. Mary and John, and any other figures, are shown facing towards Christ with their hands raised in supplication on behalf of humanity.”
Read the rest, from Wikipedia on “Deesis.”
The mosaics of Emperor Joannes I Comnenos and Empress Irene and Alexius II. The Emperor is holding a purse in his hand as a symbol of an imperial donation to the church. The Empress is holding a scroll in her hand with the inscription Pious Augusta Irene.