What are the kinds of magic we see in the Warcraft setting?
Well, for starters, there's the magic performed by practitioners of the Holy Light, most priests and paladins. This magic comes from the same source as the power the naaru draw from and seems inherent in all living things. Then there's the somehow related shadow magics of shadow priests, which the naaru also tap into during their life cycle. Warlocks also seem capable of touching upon this shadowy magical energy, as do necromancers to varying degrees. This magic seems to derive from a clash of cosmic forces of light and darkness.
However, these are hardly the only forces of magic in the cosmos of the Warcraft setting. Mages tap into the magic that suffuses the material plane, which is generally known as arcane magic and which is the power the original Well of Eternity drew from the Great Dark Beyond. Arcane magic is the closest we get to morally neutral in the setting, but it does pretty much whatever the person using it can figure out a spell to make it do. This makes it incredibly seductive, and those who learn it often become obsessed with it. Its lure is so strong, in fact, that it even draws the attention of the demons of the Burning Legion. And the Legion is hardly without magic of its own.