From the OCA.org website...
In the Orthodox Christian Tradition the "bodiless powers" are involved in every aspect of worship. The ranks of the bodiless Heavenly Powers are called angels, each having its own name and position of service. The Lord appointed the Holy Archangel Michael (his name in Hebrew means "who is like unto God"), the faithful servitor of God, as Chief Commander over all the Nine Ranks. Archangel Michael cast down Lucifer and the other fallen spirits to Earth when they rebelled against God in Heaven.
The Greek word angel means "messenger", which is shown by depicting them with wings in Iconography. Other messengers, such as John The Baptist, have also been depicted with wings.
The Archangel Gabriel spoke to Mary when she was told that she would give birth to Christ. Angels spoke the shepherds after Christs birth and sat in the tomb of Christ speaking to the ointment bearing women about his glorious resurrection. The Angels themselves warned St. John, as seen in the book of Revelation, not to worship Angels, but to worship God only.
Also taught in Orthodox Christian Tradition is that each person has a guardian angel, and that every nation also receives its own guardian angel from God (Dan. 10:13).
The Angelic Ranks are divided into three choirs: highest, middle, and lowest.
The Highest Choir includes: the Seraphim, Cherubim and Thrones.
The six-winged SERAPHIM (Flaming, Fiery) stand closest of all to the Most Holy Trinity. They blaze with love for God and kindle such love in others.
The many-eyed CHERUBIM (outpouring of wisdom, enlightenment) (Genesis 3:24) stand before the Lord after the Seraphim. They are radiant with the light of knowledge of God, and knowledge of the mysteries of God. Through them wisdom is poured forth, and people's minds are enlightened so they may know God and behold His glory.
The THRONES (Colossians 1:16) stand after the Cherubim, mysteriously and incomprehensibly bearing God through the grace given them for their service. They are ministers of God's justice, giving to tribunals, kings, etc. the capacity for righteous judgment.
The Middle Angelic Choir consists of three Ranks: Dominions, Powers, and Authorities:
DOMINIONS (Colossians 1:16) hold dominion over the angels subject to them. They instruct the earthly authorities, established by God, to rule wisely, and to govern their lands well. The Dominions teach us to subdue sinful impulses, to subject the flesh to the spirit, to master our will, and to conquer temptation.
POWERS (1 Peter 3:22) fulfill the will of God without hesitation. They work great miracles and give the grace of wonderworking and clairvoyance to saints pleasing to God. The Powers assist people in fulfilling obedience's. They also encourage them to be patient, and give them spiritual strength and fortitude.
AUTHORITIES (1 Peter 3:22, Colossians 1:16) have authority over the devil. They protect people from demonic temptations, and prevent demons from harming people as they would wish. They also uphold ascetics and guard them, helping people in the struggle with evil thoughts.
The Lowest Choir includes the three Ranks: Principalities, Archangels, and Angels:
PRINCIPALITIES (Colossians 1:16) have command over the lower angels, instructing them in the fulfilling of God's commands. They watch over the world and protect lands, nations and peoples. Principalities instruct people to render proper honor to those in authority, as befits their station. They teach those in authority to use their position, not for personal glory and gain, but to honor God, and to spread word of Him, for the benefit of those under them.
ARCHANGELS (1 Thessalonians 4:16) are messengers of great and wondrous tidings. They reveal prophecies and the mysteries of the faith. They enlighten people to know and understand the will of God, they spread faith in God among the people, illuminating their minds with the light of the Holy Gospel.
ANGELS (1 Peter 3:22) are in the lowest rank of the heavenly choir, and closest to people. They reveal the lesser mysteries of God and His intentions, guiding people to virtuous and holy life. They support those who remain steadfast, and they raise up the fallen. They never abandon us and they are always prepared to help us, if we desire it.
Holy Scripture and Tradition give us the names of the Archangels:
Michael: ("who is like unto God"), the faithful servitor of God, Chief Commander of The Army of Heaven.
Gabriel: strength (power) of God, herald and servitor of Divine omnipotence (Daniel 8:16, Luke 1:26). He announces the mysteries of God.
Raphael: the healing of God, the curer of human infirmities (Tobit 3:16, 12:15)
Uriel: the fire or light of God, enlightener (3 Ezdras 5:20). We pray for him to enlighten those with darkened minds.
Selaphiel: the prayer of God, impelling to prayer (3 Ezdras 5:16). He prays to God for mankind.
Jehudiel: the glorifying of God, encouraging exertion for the glory of the Lord and interceding for the reward of efforts.
Barachiel: distributor of the blessings of God for good deeds, entreats the mercy of God for people.
Jeremiel: the raising up to God (3 Ezdras 4:36)
In Iconography (pictures) the Archangels are depicted in according to the character of their service:
Michael tramples the devil underfoot, and in his left hand holds a green date-tree branch, and in his right hand a spear with a white banner (or sometimes a fiery sword), on which is outlined a scarlet cross.
Gabriel with a branch from Paradise, presented by him to the Most Holy Virgin, or with a shining lantern in his right hand and with a mirror made of jasper in his left.
Raphael holds a vessel with healing medications in his left hand, and with his right hand leads Tobias, carrying a fish for healing (Tobit 5-8).
Uriel in his raised right hand holds a naked sword at the level of his chest, and in his lowered left hand "a fiery flame."
Selaphiel in a prayerful posture, gazing downwards, hands folded on the chest.
Jehudiel holds a golden crown in his right hand, in his left, a whip of three red (or black) thongs.
Barachiel is shown with a white rose on his breast.
Jeremiel holds balance-scales in his hand.
Forgive me...