What are the major concepts of American government?

Three major concepts define American government. First, it is a representative democratic type of government, outlined in and enforced by the Constitution of the United States, that serves the will of the people and gives them direct access to their government through the political process. Second, it is federal, with the powers divided between a central government and several local governments. Third, it is limited in nature, in that the government does not have ultimate authority over the people, and each individual has certain rights that the government cannot take away. Associated with its limited nature is the government's power distribution, which is divided among its three branches and kept in place by a system of checks and balances. Together these concepts ensure that the American government lies in the hands of the people.

source:The Handy Politics Answer Book by Gina Misiroglu,page 14