What's the difference between a windmill and a wind turbine?

Windmills have been in use since the 9th century and use the kinetic energy (energy of motion) of wind to do mechanical work, like crushing grain or pumping water.

Wind turbines use a generator to transform the kinetic energy of the wind into electricity without producing any greenhouse gases. The generator is essentially a magnet that creates an electrical current in a coil of wires when it spins.