In most cases there is little to differentiate a wizard from similar
fictional and folkloric practicioners of magic such as an enchanter, a magician,
a sorcerer, or a thaumaturgist; however specific fantasy authors and FRPGs
use the names with narrower meanings. When such distinctions are made, sorcerers
are more often evil, "black magicians" (i.e., practitioners of
black magic), and there may be variations on level and type of power associated
with each name.
For example, Dungeons & Dragons Third Edition (D&D3E), distinguishes
between sorcerers and wizards: "Sorcerers create magic the way poets create poems, with inborn
talent honed by practice."
"Wizards depend on intensive study to create their magic. ... For a
wizard, magic is not a talent but a deliberate rewarding art."
Another example: "The difference between a wizard and a sorcerer is
comparable to that between, say, a lion and a tiger, but wizards are acutely
status-conscious, and to them, it's more like the difference between a lion
and a dead kitten." (Steve Pemberton, The Life & Times of Lucifer
Jones)
Lyndon Hardy's Master of the Five Magics suggests ascending ranks of
thaumaturgist, alchemist, magician, sorcerer, and wizard.