### Instruction:
What is a dam?

### Response:
A dam is a barrier that stops the flow of water of a river and creates an artificial lake. Dams are used for different reasons. Some dams are used to gather water for industrial, agricultural needs or water supply to civil aqueducts. Another usage can be for power generation employing hydroelectric turbines. Some other times, it is mean of water flow control aimed at flood prevention or land reclamation.