A unitary state is one which is not made up of territorial divisions, which are states by themselves. The central government is all powerful. Unitary State is also known as a simple state. A composite state is one which is itself a group of constituent states. There are two types of composite state, if it consists only one region is called non-orthogonal composite state. If composite state have two or more than two regions is called orthogonal composite state.
The difference between unitary state and composite state states rests on legislative power. In the case of unitary state there are no territorial divisions. It is composed of one unit and there is only one central authority having supreme legislative power i.e. there is no division of powers between the national government and the local government under the Constitution. The national government holds a paramount position in administration throughout the country. For instance, in Britain, France, Spain, Turkey etc.
In case the powers of government are constitutionally divided between the central and the regional units that will be called a composite state which is composed of a number of units put together. In Pakistan these are named provinces, in America they are called states.