What is the difference between fiat money and representative money?

the difference between representative money and Fiat money is that?A)representative money can be converted into silveror gold;fiat money cannot.B)representative money is worth more per dollar than fiat money; which is actually worthless.C)fiat money is counted in coins; representative money is counted in paper.D)fiat money is mre traditional than representative money,which is a newer concept. :)