The Governor is the head of a state, just as the President is the head of the republic. He is the nominal head of a state, while the CM is the executive head.
All Executive actions in the state are taken in the name of the Governor. However, in reality he merely gives his consent to the various executive actions. The real powers in the executive dealings of a state rest with the Chief Minister and the Council of Ministers.
According to an amendment in the Constitution of India, brought about in 1956, the same person can be the Governor of two or more states.
Apart from the governors in the states, Lieutenant-Governors are appointed in the Union Territories of Delhi, the Andaman and Nicobar Islands and Pudducherry.
All other union-territories are governed by an Administrative Head (an IAS officer). The only exception is Chandigarh. The governor of Punjab is also the lieutenant governor of Chandigarh.
The powers of the Lieutenant Governor of a union-territory are equivalent to the powers of a Governor of a state in India. Both are appointed by the President of India for a term of 5 years.