what is the main feature of a federation
Federation A federation (also known as a federal state) is a political entity characterized by a union of partially self-governing states or regions under a central (federal) government. In a federation, the self-governing status of the component states, as well as the division of power between them and the central government, is typically constitutionally entrenched and may not be altered by a unilateral decision of either party, the states or the federal political body. Alternatively, federation is a form of government in which sovereign power is formally divided between a central authority and a number of constituent regions so that each region retains some degree of control over its internal affairs.[1][2]
Federal republic In a federal republic, there is a division of powers between the federal government, and the government of the individual subdivisions. While each federal republic manages this division of powers differently, common matters relating to security and defense, and monetary policy are usually handled at the federal level, while matters such as infrastructure maintenance and education policy are usually handled at the regional or local level. However, views differ on what issues should be a federal competence, and subdivisions usually have sovereignty in some matters where the federal government does not have jurisdiction. A federal republic is thus best defined in contrast to a unitary republic, whereby the central government has complete sovereignty over all aspects of political life. This more decentralized structure helps to explain the tendency for more populous countries to operate as federal republics.[2] Most federal republics codify the division of powers between orders of government in a written constitutional document.