It is an ideal from our founding fathers. They had just been through a period of harsh rule under British government and as they began to create the documents and articulate the ideals that our great nation was built upon, they needed to convey these thoughts to the masses. (Granted, they spoke differently then than they do to us today.) Essentially, the speaker(s) meant that when any ONE group, be it a party or a government, has control without checks and balances from outside it is very easy for that ONE group to make all the rules, approve all the rules and enforce all the rules any way they see fit regardless of the will of opposition. To avoid this problem, we created a three-branch government; the President has the Executive responsibilities meaning he is the chosen leader of the people and can void anything done by the Congress which is the Legislative branch since they make the laws and the Supreme Court has judiciary responsibilities meaning they take an oath to ensure that the President and Congress cannot pass laws that go against our Constitution. That's checks and balances. No one single branch of the government is more powerful than the others and to get things done according to the will of the people in accordance with our Constitution, all three must agree to some extent. Its a safeguard against tyranny.