From the Big Fat Book Of Magicalia: Edition 1- General

Angels are the polar opposite of demons, being birthed from the light of the gods that created the known universe. They act as voices for the gods and are separated into species based on whom they speak for. Angels can also be wished into existence if a species of intelligent creatures worship a god that does not exist. These are also a species.

They all are capable of flight, have amazing self regenerative abilities, and have incredible light magic capabilities.

All angels have the ability to summon a mysterious beam of concentrated energy which can have multiple properties. It may manifest in the form of a beam of fire, a waterfall, or simply light, but the intention of summoning the beam results in its effects. If intended for support, it will heal anyone within its area of effect. If used for battle, it causes massive burns in the area of effect, which can kill. 

Angels have an remarkable affinity for symbolic magic, often using their god's sign to grant themselves or others protection and healing, as well as cleansing rituals, conjuring other angels, and banishing/killing demons.

Specific angels are assigned to churches to give premonitions to priests that are deemed worthy. Others are assigned to protect and heal charges to keep evil from killing harbingers of good and forcing the balance of the universe to evil.

Angels can be summoned by harming an charge or simply invoking them. You may get a different angel than you wished based on your beliefs, but most are benevolent towards whoever summoned them. 

All angels have holy counterparts called dark angels. These are not evil angels as their names may suggest, but rather angels that are capable of dark magic. They are assigned to witches with dark magic to help them keep the darkness from consuming them.