Unitary Government: Power is almost entirely centralized in a national Government. Power devolves to local Governments only for the sake of convenience (such as garbage collection times or issuing parking tickets). Any local Governments that exists hold power only with permission from the national Government, and they cannot ever conflict with national policy. Thus, in the UK, the counties into which England is divided have their own bureaucracies and regulations, but only in areas where the national Parliament has given them permission to set up those systems. Unlike a Federal system, there are no reserved powers for states or provinces.
Local power may be granted by the national legislature, but it can be modified or revoked. Unitary nation-states might set up regional Governments, but only to handle regulations that might be too burdensome to control entirely from a nationwide bureaucracy. Unitary Governments are relatively common.
Federal Government: The central (or federal) Government controls more trade policy, and makes decisions about policy areas that involve interactions between states (such as highway systems). It usually has the power to tax independently of the states and to control the money supply. A Federal Government also usually has its own mechanisms for enforcement. For example, in the USA, the FBI is the primary agency for investigating Federal crimes and crimes that occur between or among multiple states.
The Royal Canadian Mounted Police have a similar function in Canada. Federal systems (or federations) are more common than Confederal Governments today. The USA, Germany and Canada are Federal, and Russia is a rather centralized federation. Federal systems differ in how much power they give to the Federal, as opposed to the regional Governments, but they are all alike in that some powers are reserved at each level of Government in a balancing act.
