h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

A Wizard's true purpose is to act as a conduit for Natural Magic, controlling the flow of magical forces throughout Nature & directing it towards its proper place in its proper realm. A Sorcerer/Sorceress has no true purpose other than one of his/her own choice.
A Wizard receives his/her power from the Trapped Magic of Nature, which is a part of God's power. A Sorcerer/Sorceress enlists the aid of evil spirits & demons to acquire their ability to use Forbidden Magic (Sorcery), or uses knowledge from Wizards for their own purposes.
A Wizard forsakes the trappings of wealth & power. A Sorcerer/Sorceress usually desires more wealth & power.
A Wizard maintains & replenishes the flow of Natural Magic which he/she uses, leaving the natural condition of his/her surroundings unscatched or livelier than before. A Sorcerer/Sorceress drains the Natural Magic from his/her surroundings heartlessly, leaving stagnation & decay in their wake.
There is no such thing as an EVIL Wizard. Wizards who turn bad (like Saruman in 'Lord Of The Rings') are automatically called Sorcerers & Sorceresses.
Wizards are not to be underestimated through physical means as they're much stronger than mere mortals. Roaming from one realm to another while carrying a satchel laden with everyday-life essentials & a staff in hand requires more strength, stamina, endurance, agility & concentration than a normal human can produce. They can also jump very high. Sorcerers/Sorceresses, who do not have much of a need to travel or have their own minions to do it for them, have less exercise & are therefore physically weak by nature. But don't be so bold as to challenge a Sorcerer/Sorceress in hand-to-hand combat, as with a single spell they can take the manifestation of The Rock or Chyna.