Federalism is a form of governance which revolves around power sharing between a general government at the centre (federal' government) with regional governments (provincial, state, cantonal, territorial or other sub-unit governments) in a single political system. The USA is an example of the federal government.
In a system where the central government is supreme and has authority over the decision making for all subordinate local governments is called a Unitary Government. The United Kingdom overseeing Scotland is an example of this type of governance.
Thus for a unitary government, all powers lie with the central government, but in the federal government, the power is divided between two tiers of the government at the federal and local level that connects to the national government.