Magic refers to the capability of any sufficiently intelligent person to create, destroy and change matter and energy. It is thought that this power was once locked away within the minds of the greater races, but that some great event burnt away the barriers that prevented them from using it.
Often incorrectly thought to be a gift from the gods, magic is a force that is created and maintained by the will of the practitioner. It requires a focus, which is why it is often used in conjunction with the gods, faith playing the part of focus. In other words, instead of the much more difficult task of willing power into being, most practitioners approach it in the sense of “I shall channel this gift.” rather than “I shall create fire from my brain!” as an unskilled practitioner is likely to just straight up set their brain itself on fire.
Magic is a puzzling thing because by-in-large, it defies all physical logic, but, despite what many less informed scholars attest to, magic is a force that consumes resources like anything else. The difference is that unlike things like fire and electricity, the medium that it feeds upon and is channeled through is produced and maintained by the mental power of those using it. Unfortunately this means that a loss of focus or conviction will often derail any magic being used. This is why those who use such power train with it. Anyone can use magic, but few can do more than accidentally set themselves on fire.
The thing that both the religious authorities and magical scholars alike prefer not to address is that for those not using faith as a focus, magic is only as difficult to use as the person using it thinks that it is, and is based far more upon imagination than any sort of physical power. That said, the more mental strain one puts themselves under, the more likely they are to make a mistake and horrible eviscerate themselves.