Angels often appeared to people in the Old Testament bringing messages from God. The word angel means "messenger" and this word expresses the nature of angelic service to the human race. Angels are also referred to as "bodiless Powers of Heaven." Angels are organized into several orders, or Angelic Choirs.
Theophany (from Greek theophania, meaning "appearance of God") is a word sometimes used to describe an appearance of God in the form of angels. For example, the icon of the Holy Trinity (or Angels at Mamre) shows God's appearing to Abraham in the form of three angels.