Comments - J3loodT4lon

The way I see it is this:

Shamanism (both 'light' and dark) get their magic from elementals and spirits, with dark shamans forcing elementals and spirits into submission while 'light' shamans ask for their aid, and could very well be denied.

Arcane magic utilizes ley lines and the lifeblood of Azeroth herself to generate the desired effects, by using verbal, somatic, and possibly even material components and channeling arcane through themselves to create the spells.

Death, Shadow, and Fel magic would arguably fall under the blanket category of Black Magic, however their source of power is different. Death magic is anything that would fall under the category of necromancy. It pertains to Death, and everything directly related to it. Shadow magic is derived from the shadow plane, and its inhabitants, and Fel magic is derived from the Twisting Nether. So while they would all be considered Black Magic, it is still important to differentiate between the different types of Black Magic, as each type has its own source and potential drawbacks.

In terms of the difference between Light and Life, while I am not entirely certain and could very well be incorrect, I do believe the difference between them is Light magic is just that: Light magic. It is derived from whatever Holy entity it is that grants Paladins and priests their abilities, like the Naruu (who are beings of pure holy energy). Life magic has is roots (pun intended) in Nature magic. Their uses most certainly do overlap, but just as the 'black' magics, there is a very important distinction in the form of that magic's origin.