The Simple English Wikipedia definition :
Wind turbines use the kinetic power of the wind to generate electricity. Historically, they were more frequently used as a mechanical device to turn machinery.
There are two main sorts of wind generators : those with a vertical axis and those with a horizontal axis.
Here are the 3 main types of wind turbines :
HAWT / VAWT = horizontal / vertical axis wind turbines
updated November 25, 2011