Mages and Wizards: These are technically two different classes on my world, but are set up pretty much the same way. They are people who study the arcane and wield magical energies like some people wield swords. They can wear only cloth armor, anything else will hinder their spell casting. They use staves and daggers, but not many martial weapons. They gain all the knowledge skills as class skills with a +3, (though they have to pick what their local knowledge would be at). Some have familiars, creatures who help them with their magic, but they do not need them to be the most powerful they can be.
The major difference between mages and wizards comes from where they gain their power. Targon rules the mages, and so most mages use only good or neutral energies to cast their spells. They do not drain life energies or work with undead. Where as wizards gain their spell magic from Kahalla and work almost exclusively in necromancy. In game terms wizards would be necromancers, while mages would be all other arcane schools. Mages aren't bared from necromancy, they just can't use anything that deals with undead or draws from others. Cause Fear and Chill Touch would not be bared to Mages, (though they would be harder for them to cast), but Command Undead would definitely be off a Mages spell list. Any necromancy spell uses a spell slot one level higher for a mage to cast. Wizards can cast all mage/wizard spells, but anything which brings life, such as the spell False Life in Pathfinder, they would find hard to cast. (Has to be cast using a spell slot one level higher). Wizards are always some sort of evil, where mages can be good or neutral.