Dear Student
A Windmill is a machine which converts the energy of wind into rotational energy by means of vanes called blades. It can be used for variety of purposes such as generating electricity or run machinery etc.
Windmills use blades to gather wind that flows over it. Windmills use their blades for lift , in this case to turn the windmill. Windmills are very simple structures ,their blades are connected to a drive shaft that is connected to an electric generator. As the blades turn, this turns the drive shaft and creates electricity. Electricity is sent through wires and collected.
Regards