A Government Security (G-Sec) is a tradeable instrument issued by the Central Government or the State Governments. It acknowledges the Government’s debt obligation.
Such securities are short term (usually called treasury bills, with original maturities of less than one year) or long term (usually called Government bonds or dated securities with an original maturity of one year or more).
In India, the Central Government issues both, treasury bills and bonds or dated securities
The State Governments issue only bonds or dated securities, which are called the State Development Loans (SDLs).
G-Secs carry practically no risk of default and, hence, are called risk-free gilt-edged instruments.