The most common type of dam is an impoundment hydroelectric plant, which consists of a dam across a river, and a reservoir (lake) behind the dam. How does this type of dam work

A turbine spins the water to generate electricity.

Explanation:

This is impoundment facility is called a hydro electric power dam, it is basically a big hydropower system which uses the dam to store river water in a reservoir. The water released from the reservoir flows directly through a turbine, the turbine spins it, which afterwards activates a generator to generate electricity.