A shilling is an old British coin, roughly equal to a nickel. Twenty shillings were equal to one pound.
The shilling isn't used any more in Great Britain, although other countries, like Uganda and Kenya, still use shillings. It was a small silver colored coin with a small value, similar to the nickel in the United States, that was used from the 1500's until Britain decimalised its currency in 1971 and stopped making shillings. The popular nickname for a shilling was a "bob."