Montesquieu wanted a political system of government in which the powers are separated. According to his views the Executive should perform the task of running the government ;the Legislature should perform the task of law making and the Judiciary should check whether these laws are being correctly imposed or not.On these notions ,the parliamentary system of government is based upon.
Separation of powers is that each organ of the state should have its own functions. For instance the judiciary should not be involved in law making , that is the function of the legislature . Montesquieu's theory supports this view.
Montesquieu used the separation of powers in the form of the judicial, legislature, and executive branches to balance the power throughout the government. His intentions was to protect the freedom of the people. In order to keep these three branches in place he allowed each their own job, and gave them permission to veto each others acts. In the 18th Century the English Parliamentary used this principle to form a stable government.