The first group of angels consists of those who are in God’s presence and are said to be directly and immediately one with Him: the Seraphim with their six wings, the many-eyed Cherubim and the holiest Thrones.
An angel, then, is an intelligent essence, in perpetual motion, with free-will, ministering to God, having obtained by grace an immortal nature. It is not susceptible of repentance because it is incorporeal. For it is owing to the weakness of his body that man comes to have repentance.
They are secondary intelligent lights derived from that first light which is without beginning, for they have the power of illumination; they have no need of tongue or hearing, but without uttering words they communicate to each other their own thoughts and counsels.
Based on St. John of Damascus
In the photo, a candid moment from Divine Leiturgy near to the Holy Altar at Vatopaidi.