RBI is the Reserve Bank of India. It is the governmental institution since Independence, although it was started as a private institution.
It is a member of Asian clearing house. That for clearing and exchange of international cheques and currencies etc.
RBI controls the monetary policies related to Rupee. It is the central bank for the government of India. It advises government and various nationalized bank on the assets, interest, loans and other matters. It frames regulations that banks must follow.
RBI monitors various public and private banks and financial institutions.