ELI5: Explain Like I'm 5

Windmill

A windmill is a machine that harnesses the power of the wind for lots of different tasks. It has four big blades which turn around in the wind, like a fan. This turning makes a special machine inside the windmill spin, and this spinning makes energy that can be used for different things. This energy can be used to turn big machines like those used to grind grains, or it can be used to generate electricity.