Answer:
Seperation of power is a doctrine of constitutional law under which the three branches of government are kept separate (the executive,legislative and judicial). The executive branch Executes and enforces laws, the legislative branch proposes laws and confirms nominations for federal officials, the judicial branch which includes the supreme court can declare war and settles legal disputes.
This is important since it evenly distributes power instead of having one person (the president) have all of the power. This prevent the abuse of power of one person. The fathers of our nations thought of this since they didn't want another king to rule over them.
Explanation: