I do not really understand what an angel is. I regard one as a presence of God. Can someone enlighten me?
Here’s a passage from the Catechism of the Catholic Church about the angels:
I. THE ANGELS
The existence of angels - a truth of faith
328 The existence of the spiritual, non-corporeal beings that Sacred Scripture usually calls “angels” is a truth of faith. The witness of Scripture is as clear as the unanimity of Tradition.
Who are they?
329 St. Augustine says: "‘Angel’ is the name of their office, not of their nature. If you seek the name of their nature, it is ‘spirit’; if you seek the name of their office, it is ‘angel’: from what they are, ‘spirit’, from what they do, ‘angel.’"188 With their whole beings the angels are servants and messengers of God. Because they “always behold the face of my Father who is in heaven” they are the “mighty ones who do his word, hearkening to the voice of his word”.189
330 As purely spiritual creatures angels have intelligence and will: they are personal and immortal creatures, surpassing in perfection all visible creatures, as the splendor of their glory bears witness.190
Christ “with all his angels”
331 Christ is the center of the angelic world. They are his angels: "When the Son of man comes in his glory, and all the angels with him. . "191 They belong to him because they were created through and for him: "for in him all things were created in heaven and on earth, visible and invisible, whether thrones or dominions or principalities or authorities - all things were created through him and for him."192 They belong to him still more because he has made them messengers of his saving plan: "Are they not all ministering spirits sent forth to serve, for the sake of those who are to obtain salvation?"193
332 Angels have been present since creation and throughout the history of salvation, announcing this salvation from afar or near and serving the accomplishment of the divine plan: they closed the earthly paradise; protected Lot; saved Hagar and her child; stayed Abraham’s hand; communicated the law by their ministry; led the People of God; announced births and callings; and assisted the prophets, just to cite a few examples.194 Finally, the angel Gabriel announced the birth of the Precursor and that of Jesus himself.195
333 From the Incarnation to the Ascension, the life of the Word incarnate is surrounded by the adoration and service of angels. When God "brings the firstborn into the world, he says: ‘Let all God’s angels worship him.’"196 Their song of praise at the birth of Christ has not ceased resounding in the Church’s praise: "Glory to God in the highest!"197 They protect Jesus in his infancy, serve him in the desert, strengthen him in his agony in the garden, when he could have been saved by them from the hands of his enemies as Israel had been.198 Again, it is the angels who “evangelize” by proclaiming the Good News of Christ’s Incarnation and Resurrection.199 They will be present at Christ’s return, which they will announce, to serve at his judgment.200
Later the Catechism summarizes:
350 Angels are spiritual creatures who glorify God without ceasing and who serve his saving plans for other creatures: “The angels work together for the benefit of us all” (St. Thomas Aquinas, STh I, 114, 3, ad 3).
351 The angels surround Christ their Lord. They serve him especially in the accomplishment of his saving mission to men.
352 The Church venerates the angels who help her on her earthly pilgrimage and protect every human being.
scborromeo.org/ccc/p1s2c1p5.htm
To clarify, while the term “angel of the Lord” is sometimes used in the Old Testament to apparently refer to a manifestation of the presence of God, what we commonly call angels are these personal, rational, spiritual creatures which are distinct form and created by God.
