(Latin angelus; Greek aggelos; from the Hebrew for "one going" or "one sent"; messenger)
The angels are represented throughout the Bible as a body of spiritual beings intermediate between God and men: "You have made him (man) a little less than the angels". They, equally with man, are created beings and they are spirits.
They are attendants at God's throne and God's messengers to mankind. They are His instruments by whom He communicates His will to men.
They take care of every human being (as guardian or tutelary angels) but somtimes they are represented as the constituted guardians of the whole nations (e.g. at some particular crisis)
It is the angels who put into execution God's law regarding the physical world.
At the beginning people believed that angels were visible until St. Thomas published the thesis that they are spiritual beings only and therefore invisible.