what is a angel?

Answer 1

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.'"

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."

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.

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.'" (Heb 1:6)

Their song of praise at the birth of Christ has not ceased resounding in the Church's praise: "Glory to God in the highest!" (Lk 2:14)

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. (Cf. Mt 1:20; 2:13, 19; 4:11; 26:53; Mk 1:13; Lk 22:43; 2 Macc 10:29-30; 11:8)

Again, it is the angels who "evangelize" by proclaiming the Good News of Christ's Incarnation and Resurrection. (Cf. Lk 2:8-14; Mk 16:5-7)

They will be present at Christ's return, which they will announce, to serve at his judgment. (Cf. Acts 1:10-11; Mt 13:41; 24:31; Lk 12:8-9)

With love in Christ.

Answer 2

The original Greek translation for angel is messenger of God.