A dam has a big wall made of concrete. This wall dams up a river and turns it into a large lake. Most dams are built to generate electricity from the power of water.
Imagine: A mill wheel standing in a stream is turning. This is because the power of the flowing water is transferred to the mill wheel. A dam works in a similar way. The pressure of the dammed water behind the dam wall causes the water to flow very quickly and with great force through tubes in the dam. At the end of the tubes, the water meets turbines that are set in motion by the water in a similar way to a mill wheel. These turbines are connected to generators that produce electricity from the rotary motion. This is how electricity is generated from water power. Electricity is very important to all of us. Without electricity, your mom would oversleep in the morning because her cell phone alarm clock wouldn't ring. And your dad wouldn't know how to shave off his stubble without an electric razor. In the kitchen, the refrigerator would defrost. And you would be sitting in your children's room in the dark in the evening.
In a nutshell.: Dams are built to generate electricity from the power of water.
