Separation of Power is a concept in political science that refers to the division of governmental responsibilities into distinct branches to limit any one branch from exercising too much power. This is often done through the creation of checks and balances among the branches of government.
Montesquieu's theory:
Montesquieu, a French philosopher of the 18th century, is often credited with the theory of separation of powers. According to Montesquieu's theory, “the powers of government should be divided into three separate branches: the legislative, the executive, and the judiciary. Each branch should have a distinct function, and each should be independent of the others, with no one branch having too much power or control.”