Federation
A federation is a union of a number of self-governing states or regions, which are joined together under a central government. The central government is not able to do a lot of things that central government in more centralized states can. These things are done by the states (or regions) in a federalized state.
The United States of America is a federation. The federal (central) government has the highest executive role. However, state governments can exercise any powers as long as those powers are not assigned to the federal government (by the United States Constitution) and if those powers are not prohibited by the states themselves.
Australia became a Federation in 1901.
After the 1971 civil war, Pakistan became a Federation adopted in the 1973 Constitution of Pakistan.
Other examples of federal states are Austria, Belgium (since 1993), Canada, Germany, Russia and Switzerland.
Federation Media
Federal states* Unitary states
A map of the Russian Federation, showing its eighty-three federal subjects before the annexation of Crimea in 2014
A map of Brazil, showing its twenty-six constituent states and the Federal District
A map of the Federal Democratic Republic of Ethiopia, showing its regions
A map of the Federal Republic of Nigeria, showing its 36 states and the Federal Capital Territory
A map of the United Mexican States (Mexico), showing its thirty-one constituent states and Mexico City
A map of the United States of America showing its fifty constituent states and the District of Columbia
A map of Canada showing its ten provinces and three territories
A map of Australia showing its six states and ten territories