Impoundment

Impoundment is the most common type of hydropower plant, which uses a dam to hold a large volume of river water in a reservoir. This large volume of water then flows through a channel to the turbine near the bottom of the dam. This high velocity water then turns a turbine that spins a generator to generate electricity.

dam
Photo Taken From Here

Diversion

The diversion method of hydroelectric energy generation is very similar to the impoundment method, however instead of using a dam, a portion of the river is diverted into a channel that flows directly into the turbine.

Pumped-Storage Facility

This type of hydroelectric energy generation stores energy for later use, similar to a battery. Energy is used to pump water from a low elevation river to a reservoir at a higher elevation with energy gathered from hydropower, or any other type of power generation. Large volumes of water are stored in the reservoir until a high amount of electricity is needed, when this happens, the reservoir is released through a turbine system that generates the needed electricity.

Linked is an informative video produced by energy.gov.