Q: What are national emergency, state emergency and financial emergency ?

Ans: National Emergency under Article 352 :  A national emergency modifies the quasi-federal system of government to a unitary one by granting Parliament the power to make laws on the 66 subjects of the State List (which contains subjects on which the state governments can make laws). Also, all state money bills are referred to the Parliament for its approval. 

During an emergency, the term of the Lok Sabha can be successively extended by intervals of up to one year, but not beyond six months after the state of emergency has been revoked.

Emergency can only be declared on grounds of "External aggression or war", also called as External Emergency & on the ground of "armed rebellion", also called as Internal Emergency. The President can declare such an emergency only on the basis of a written request by the Cabinet headed by the Prime Minister.

State Emergency under Article 356 : 

Emergency due to the failure of the constitutional machinery in the states. This is popularly known as President’s rule. It is also known as ‘State emergency’ and ‘Constitutional emergency’.

Financial Emergency: Article 360: Financial Emergency due to a threat to financial stability or credit of India