Question: What is the difference between Angels and Archangels?  

Answer: “You should be aware that the word ‘angel’ denotes a function rather than a nature. Those holy spirits of heaven have indeed always been spirits. They can only be called angels when they deliver some message. Moreover, those who deliver messages of lesser importance are called angels; and those who proclaim messages of supreme importance are called archangels. “Some angels are given proper names to denote the service they are empowered to perform. Personal names are assigned to some, not because they could not be known without them, but rather to denote their ministry when they come among us. Thus, Michael means ‘Who is like God?’ Gabriel is ‘The Strength of God’; Raphael is ‘God’s Remedy.’”     –St. Gregory the Great (540-604), Homily.