What are 'checks and balances'?

Checks and Balances, as it is referred to in the American system, is a system of limiting power which allows the branches of government to put a 'check' on one another in order to stop political domination. It means that for every power afforded to a branch, there is a 'check' on the power; that is to say a limit of some shape or form that stops the branch from wielding too much political power.

For example, the Executive Branch (President and Executive) have the power to send troops to conflict; this is balanced by Congress (Legislative Branch) who, under the War Powers Act, must be informed of this within 60 days and can comment on and potentially stop the advancement of troops. Similarly, after legislation has passed through both houses of Congress, the President can use his Power of Veto to ensure the legislation does not go through. Additionally, the judicial branch (Supreme Court and judiciary) can examine the legislation passed by both aforementioned branches, ascertain their Constitutionality and debate over them.