Nowadays almost everybody with something besides your clothing you wear has some money from all forms of wealth money is the most widespread, indeed in a modern economy is virtually impossible to live without it. The keynote of complex economic systems of our time is the especialização.Com the march of economic development, the man tends to provide a living working in some specialty and availing himself of it to pay for goods and services they consume but not produce. This process - the division of labor - contributes to the efficiency and the consequent rise in living standards. But specialization is only really possible when the medium of exchange is the currency used, real lubricant of modern market economy. Of course we can live without money. There are companies in the world in a while each family grows and produces almost all you need (food, shelter, clothing) and few economic ties with the other keeps. Also a country in advance is not uncommon for family members to pay for services they provide to each other, not the husband pays the wife for preparing the meals, nor to her husband through vegetables cultivated in this garden. In economics intrafamily all economic relations are of this type, and money is less simple desnecessário.Já are economies where transactions do not operate with the aid of money, but by the exchange or bartering of utilities. In general, the exchange takes place between families of the same core, bartering among diverse groups. Both practices admit a degree of specialization rather sharp. What prevents the adoption of the exchange system in a modern economy and complex, with huge numbers of people who participate in it, is that this type of reciprocal exchange to guarantee future depends on well-defined relationships. The obstacle to barter is to involve the direct exchange of one utility by another. Nevertheless, just as families are important economic centers in a complex society industral, also the exchange (between individuals, families or large groups) and barter (between nations) operate at a scale bulky enough to not go unnoticed. Indeed, a modern economy can meet its immediate needs exclusively through barter. It was indeed what happened for some time in Germany after the collapse of the monetary system that came to the Second World War. The interesting thing is that this emergency has been replaced by a new currency exchange instrument; cigarettes. Began to accept them in payment, not by the desire to smoke them, but because they knew they could buy with other things. Precisely the same kind of transformation must have succeeded with the first monetary systems. The common denominator was certainly not the cigarette, but maybe caurim shells, gold and silver. The fishermen could go to the market to put your fish, but instead of exchanging it for an article like fur, or hand it in trust under a tacit agreement at a future date to receive furs, silver would have been, aware of power swap it with anything else they needed. All these features are observed in even greater degree in the most modern means of transaction, such as gold and silver coins and paper money. But money is not only a medium of exchange. Agency also wealth preservation. This is certainly possible by other means, such as possession of land, securities, machines. But the coin has a very special function: it is a collection of wealth that also serves to medialize exchanges.