Federalism is a type of government where power is divided between the central or general government and the regional government. This type of government is usually characterized by a separation of powers between three tiers of government: executive, judiciary and legislative arms of government.
Federalism differs sharply from unitary and confederation form of government. In unitary form of government, power rests at the central government as opposed to the federal system where power is shared equally. In confederation systems, the states are more powerful than the central government thereby contrasting with the Unitary system of government and federal system government.
The United States's Federal system of government has been the perfect example of a federal system since America's federal system adoptment in 1776.