Type of government

A federation 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. Example- USA, Argentina, Maxsico,India

A confederation, in modern political terms, is usually limited to a permanent union of sovereign states for common action in relation to other states. Example- European Union, Switzerland, Belgium. Usually created by treaty but often later adopting a common constitution,confederations tend to be established for dealing with critical issues(such as defense, foreign affairs, or a common currency), with the central government being required to provide support for all members.

A unitary state is a state governed as one single power in which the central government is ultimately supreme and any administrative divisions (subnational units) exercise only powers that their central government chooses to delegate. The majority of states in the world have a unitary system of government. Example- UK, Ukraine, China, Cuba

The distinction between a federation and a unitary state is often quite ambiguous. A unitary state may closely resemble a federation in structure and, while a central government may possess the theoretical right to revoke the autonomy of a self-governing region, it may be politically difficult for it to do so in practice. The self-governing regions of some unitary states also often enjoy greater autonomy than those of some federations. For these reasons, it is sometimes argued that some modern unitary states are de facto federations. De facto federations, or quasi-federations, are often termed"Regional states". Example- Spain