Almost Nickie, notes where originally backed up by gold, that's why is says "I promise to pay the bearer the sum of �x" this means that x pounds of gold where stored in a bank. The note became as good s gold and hence cash was born. Now days realisable wealth is represented by what it is possible, in theory to get cash for. That is not always something physical. For example when you but a business a certain amount is in physical things but also quite a lot is in the non physical form of "good will" or "regular customers". Football club's pay millions for players that they hope will deliver skill on the pitch that is not easily quantifiable value. Your boss pays your wages on what he hopes are your abilities.