The word “angel” comes from the Greek word meaning “messenger.” According to St. Thomas Aquinas and other theologians, the myriads of angelic beings are said to be organized into nine choirs of angels, three hierarchies of three choirs each. I imagine that there are infinite sorts of angels just as there are myriad human personalities. In my experience, each Holy Angel is its own being with its own personality, and its individual, reflected Light from the Divine is recognizable and unique.