If money is a very popular subject today, it does not mean that we know it and understand its evolution. Indeed the national and international press floods us with information on the prices of different currencies, on the risk of the collapse of the euro or the dollar, there is even more and more talk about how to return to currencies national, or improve the euro. Before being able to deal concretely with local complementary currencies, it is necessary to look for a few moments on the theories of money since the 19th century.