In a federal government, power is distributed between the federal or national government and the state governments, both of which coexist with sovereignty. Under federalism, the states are not subordinate to the central government but independent of it. Federal republics further distribute the power of the national government between different branches.
National Paralegal College states that the purpose of a federal government is to allow the states a level of sovereignty, while centralizing government for affairs that affect the entire nation. Under federalism, the state and national governments typically handle different areas of politics. The federal government has authority over affairs like national security, war, coining money and international relations. The state governments are in charge of the affairs that most directly affect citizens: criminal law, birth, marriage and death records, traffic regulations and education. Whereas the Constitution only limits states insofar as they may not pass legislation contrary to what the Constitution dictates, the federal government is limited to only those actions that the Constitution specifically concedes to it.
USHistory.org describes federalism as a compromise between unitary government and a confederacy. As a result, although the states exist independently of the federal government, they are still ultimately subject to it. This distinguishes federal government from the confederate structure of the United States under the Articles of Confederation, according to which the national government was little more than an association of autonomous states.