Treasury Bill is a debt security with maturity shorter than 1 year issued under state guarantee, while Government Bond is the same security with maturity longer than 1 year. You can buy Treasury Bills / Government Bonds in order to invest your savings in medium and long term for a safe yield and return.
You can buy bonds and treasury bills through TEB Internet Banking, 444 0 666 TEB Telephone Banking or TEB Branches and hold them until maturity and get the principal sum plus interest or sell them before maturity in the secondary market.