What is the main difference between a federal form of government and a unitary one? Explain with an example.

In a federal form of government, the central government shares its powers with the various constituent units of the country. For example, in India, power is divided between the government at the Centre and the various State governments.
In a unitary form of government, all the power is exercised by only one government. For example, in Sri Lanka, the national government has all the powers.