A unitary system is governed constitutionally as one single unit, with one constitutionally created legislature. A unitary state is a sovereign state governed as one single unit in which the central government is supreme and any administrative divisions (sub national units) exercise only powers that the central government chooses to delegate.
This is one of the federal features of the Indian constitution.
The federal polity, in other words, provides a constitutional device for bringing unity in diversity and for the achievement of common national goals. A federal government exists when the powers of the government for a community are divided substantially according to a principle that there is a single independent authority for the whole area in respect of some matters and there are independent regional authorities for other matters, each set of authorities being co-ordinate to and subordinate to the others within its own sphere.
The Constitution of India has adopted federal features; though it does not, in fact, claim that it establishes a federation.
In a federal set up there is a two tier of Government with well assigned powers and functions.