Money was originally created as a way to mark an exchange of life energy between two people.
Money can have value in itself, as in gold, gems, and other precious metals.
Or, money can be a marker, such as a piece of paper or an electronic transfer, with no intrinsic value in itself. Paper money would be worthless if we did not all agree that it is a marker representing a certain value. One of the earliest uses of this kind of marker in exchange for goods happened when Mesopotamian farmers brought their grain to city granaries and stored it there, in exchange for tokens. The city kept some of the grain as payment for storage, and the farmer could trade in his tokens with merchants, who traded them for other merchandise or redeemed them for bags of grain. Gold pieces could always be melted down and made into art or jewelry.