Magic is the basic stuff of unexplained universe. A worldwide force that ebbs and surges over the course of millennia. It wa high in the Fourth World and all but non existent in the Fifth. It is rising again at the dawn of the Sixth World.
Science has been at a loss to explain magic, which functions in ways that seem to regularly defy basic unified field principles. But it does have a somewhat understandable, if fickle, internal logic related to the tropes of folklore and the structure of sympathetic mythology.
Only one child in a thousand is born with the inborn ability to manipulate magic, a disproportionate number of them Elven or pulled from tribal societies.
Most magic seems to be related to spiritual beliefs, especially old or primitive ones. That said, it is not always a matter of faith and certainly the strength of ones convictions do not seem to relate to the level of ones magical ability.
Non-magically savvy people can participate meaningfully in rituals, even gain some magical abilities for a limited time, though they never gain control over the force itself, only the after-effects.
While it is conceivable that any Mage might learn any number of powers, three kinds of specialists persist: the Adept, the Shaman, and the Technomancer