Federation is the name of a sovereign state formed by several states with autonomy of government and administration. When these entities come together through a constitution, the federation is formed, as is the case with the United States. Thus, in the Federation regime states form a central government to represent them as a federative unit in matters common to all states, such as international representation.
Confederation is similar to federation, but differs in the fact that the confederation entities are sovereign and their formation is made by alliances while in federation this is by constitution. Confederation, therefore, is a union of states created through treaties. One of the main characteristics and differences between a confederation and a federation is that in the former it does not neglect the constituent states while in the latter the authority is transferred to the federal state.