Buying and selling of government securities by the Reserve Bank of India to the public is called:

Open Market Operations  

Open market operations: It refer to the sale and purchase of government securities in open by the Central Bank.

Repo rate: The rate of interest charged by the central bank to commercial banks for a short period.

Bank Rate: Bank rate is the lending rate at which commercial banks can borrow from the RBI without providing any security. 

Margin requirement: Margin requirement is the difference between the market value of security offered by the borrower against the loan amount granted.