A watermill is a machine that uses the energy from flowing water to turn a wheel or turbine. Watermills are used to grind grain to make flour and to power machines that perform other tasks. For example, ancient watermills were used to grind grain into flour, to saw wood into boards, and even to power factories that made cloth or paper. Today, many people still use watermills to make electricity and to perform other tasks. Think of it like a wheel being spun by the energy of the water.