Money (Capital) is the basic unit of a Capitalist society
Money is not a necessity of life. People want money, to get rich, to be abe to brag about it.
Necessities of life are Food & shelter. To get Food & shelter, money is used as a medium. And that is what money is, bits of paper or metal used to exchange for Food, shelter, and things that will help you get more money like Knowledge, computer, phone, etc.
You cannot eat money nor can you protect yourself from rain with money. Money by itself is useless, if there is no one else to give it value. Your money will not have any value if all the shops/websites refuse to take it.
And, this realisation is what has given power to the Peer to Peer currency systems.