Define separation of powers. What is its importance in democracy?

because of everyone getting a say in what the rules are

the united states constitution is the supreme law of the united states. the constitution, originally comprising seven articles, delineates the national frame of government. its first three articles embody the doctrine of the separation of powers, whereby the federal government is divided into three branches: the legislative, consisting of the bicameral congress; the executive, consisting of the president; and the judicial, consisting of the supreme court and other federal courts. articles four, five and six embody concepts of federalism, describing the rights and responsibilities of state governments, the states in relationship to the federal government, and the shared process of constitutional amendment. article seven establishes the procedure subsequently used by the thirteen states to ratify it. it is regarded as the oldest written and codified national constitution in force.