Here is a comprehensive summary of the Wikipedia article on angels:

Angels are spiritual, supernatural beings in the Abrahamic religions, typically depicted as humanoid messengers with bird-like wings and halos, serving as intermediaries between God and humanity. They fulfill roles such as protectors (guardian angels) and servants of God, with hierarchical systems varying by religion—featuring named figures like Gabriel and Michael, and ranks such as seraphim and archangels. The word "angel" derives from the Greek angelos (messenger), which itself translates the Hebrew mal'akh, originally meaning simply "messenger" without any supernatural connotation. Historically, the concept emerged in post-exilic Hebrew scripture when God became seen as more distant, with angels acting as agents of both punishment and mercy, while later Zoroastrian influence introduced the idea of angels as embodiments of good opposing the Devil. Malevolent angels, known as fallen angels, are often identified with the devil or demons, while in art angels are usually portrayed as beings of extraordinary beauty—though sometimes they are rendered as frightening or inhuman. Ultimately, angels evolved from autonomous spirits in polytheistic systems into obedient servants of a single supreme deity, bridging the perceived gap between the earthly and transcendent realms.