The study of angels is actually called angelology, and is an ancient subject.
During my research I found out that angelologists believe that there are 9 orders of angels. The orders are split into groups of 3, and each group of 3 is referred to as a Triad.
The first Triad contains:
Seraphim-These are the keepers of love, and have 6 glowing red wings. They carry swords of flaming red, often referred to as the Fires of Love. They are in direct contact with God, and chant at high frequency Holy, Holy, Holy. It is said to be the vibration of Love, and the creation of Life.
Kerubim (Cherubim)- These are the keepers of wisdom and are dressed in the deepest of blue. They are often depicted as Charioteers of God, and the vibrations of their wheels echo the Seraphim, but at a lower rate.
Ophanim- the Ophanim are the chariots to the Kerubims Charioteers.
The second Triad contains:
Dominoes- these could be likened to Justice. Christians that sing Lord of Lords refer to the Dominions.
Virtues- these bestow heavenly grace and blessings via the angels of the Third Triad.
Powers- these are said to be the keepers of our souls. Their task is to prevent evil from entering the Kingdom of Heaven. It is in the sixth choir that lies the greatest risk of corruption, and therefore it is from here that we get the fallen angels.
The third Triad contains:
Principlaities- these are said to be the Governors or organizers who give strength and guidance to their nominees.
Archangels- Most faiths agree that there are at least 7 Archangels, which is one of the reasons why the number 7 is considered to be a lucky number.
Angels- these are the workforce or foot soldiers. They are trusted with the divine blessings sent from the universe to humans. The most popular angels are the guardian angels.