Dams are structures that hold back water that is later used to generate electricity. Dams can be made of earth and rocks, concrete or wood. A lake created by a dam is usually called a reservoir.

In Canada, most large dams are related to the generation of electricity. Clean, renewable hydro power is an important part of Newfoundland and Labrador's electricity system.

When it is required for hydro generation, water from the reservoir is taken through an intake to the plant where the turbines change the force of the water into electricity. The water is then released back into a river. If the reservoir becomes full before water can be used for electricity generation, the water is spilled, meaning it is bypassed around the plant and not used to generate power.