Magic is a fact of life. Dragons are very adept at its use and claim to actually be the sources of all magic in the world. Not everyone believes them, but nobody who has met a dragon disputes that they are amazingly skilled with it.
Some humans also have the ability to weild magic on their own, though most are relegated to using it vicariously by way of magically charged objects. The faculty for magic appears to be genetic, but it only sometimes passes along clear lines of heredity.