'Libor and Euribor are two of the crucial mechanisms for setting interest rates on a vast array of financial products. Libor is the largest and most variable rate, covering ten currencies. It even helps determine the rate of the US dollar in the form of eurodollars.
Traders in London, New York, Japan and elsewhere colluded to manipulate the Libor rate so as to make massive profits or conceal losses, at the direct expense of pension funds and mortgage and loan holders.'
Good explanation of LIBOR: