In the sense of federation what do you understand by the unitary government?

In this sense, federations are contrasted with unitary governments. Under the unitary system, either there is only one level of government or the sub-units are subordinate to the central government. The central government can pass on orders to the provincial or the local government. But in a federal system, the central government cannot order the state government to do something. State government has powers of its own for which it is not answerable to the central government. Both these governments are separately answerable to the people.