Magician is most often used when referring to someone that entertains using magic. An example of this would be someone practicing magic card tricks, performing illusions, or pulling a rabbit out of a hat to please a crowd. Wizard is usually used when talking about someone who practices magic, and most likely when talking about fantasy. An example would be, "Harry Potter is a wizard." :)

"Oh no sir, this wasn't built by a magician. This was built by a wizard. A man who can actually do, what magicians pretend to do." Cutter, The prestige 2006.

there is also a sorcerer - a man practicing powerful (and often dangerous) attack magic! (often connected with fire) a necromancer is a mage who deals with black magic (such as raising zombies)! a summoner is a person specializing in summoning animals, monsters or even daemons from other planes! cool, right? ))))