Although checks and balances might sound like what you would ask for at your local bank, the term actually refers to ways to make sure that no single person or organization has too much power.
A check is a way of limiting governmental actions. The presidential veto is an example of a check. A U.S. president can reject a law passed by Congress. But another check is that the law can go back to Congress, and the veto can be overridden by a two-thirds majority vote. This provides balance, so that no one branch of the government has too much power. In the U.S., federal power is divided between three independent branches: the executive (President), legislative (Congress), and judicial (Supreme Court). Having such checks and balances is a fundamental part of the U.S. government.