The given below text we have taken from OWEBMONEY.RU (and translated into English); it contains basic notions and concepts of money systems development.

The author of the text is KANTOR.

I’ll be honest with you — there wasn't any money at first. When primitive humans got the idea that separation of labour is good, they began to change goods directly. The Barter system. It seemed that everything went smooth, but the barter method has inherent problems: Supply and Demand have to match each other in time and space. To avoid this limitation, prehistoric men began using more complicated exchange schemes — I swap a mammoth's tusk for antelope's horns, which I personally don't need, because I know that a buddy from a tribe down there has a bison's hoof, which I badly need, and I'll exchange my tusk for the hoof . With time, while exchange schemes tended to be more and more refined, it became clear that there were things that matched intermediate exchange elements better and there were some that matched worse. Some goods weren't in high demand, some things lost value with time, some were too heavy or couldn't be divided in parts.

It was found out then that the gold is ideal for the sought intermediate exchange element: it was always in demand, it's valuable, it didn't lose value with time, it could be divided in parts and one can easily tell it from manure.

When gold became a universal intermediate trade agent, demand for it exceeded usual customers' demand. In the majority of cases, the gold was better accepted as paying means not because it's a material for making jewelry, but because gold can be saved as treasure, used as means of accounting and nominated as a unit of cost. The gold acquired functions of money. For better convenience, people commenced to stamp gold in small disks with a profile of a local king on them. These disks became the first currency. The golden coins were natural money, their value didn't depend on the local king's profile — they depended on the value of the gold itself.

The gold started to circulate as money.

The gold as money wasn't perfect though. It had defects, too: Heavy, wears fast (soft metal), and it should be safely kept (thieves do not sleep). Somewhere in the Middle Ages, there appeared special private shops for keeping other people's gold in safe. These shops appeared in Italy, and their names were given by Italians in Italian — banco. These bancos took gold from citizens and gave them notes — banco-notes — banknotes.

Now, when Emilio needed to pay a carpenter for a new roof, he went to his banco (bank), presented a banknote, took his gold, went back, and paid for the roof. The carpenter returned to the bank, handed over the gold, and received a banknote.

Quite soon, the idiocy of the situation became obvious: For, why should one run with gold and banknotes hither and thither, when one could give banknote to the seller, and this seller could go then to the bank and receive gold? When people understood this, they began to exchange banknotes directly — as if banknotes were gold.

At this historical point, we should note an important transformation — money ceased to be natural (dependant upon inherent value of its substratum), it became liabilities of the on who issued it (dependant upon his authority). As opposed to golden coins, it was very important to tell different faces on different banknotes, because a banknote cost the value of this or that issuer's liability.

Secured banknotes started to circulate as money.

Well then, a banker sat on a stack of gold and thought, “Why can't I earn some money lending this gold?” He knows that he's constantly haunted by people who produce banknotes to him to take their gold, but other people give him gold for keeping, and these two processes are constant. That's why he always has some gold as reserve, now lying dead weight. The banker starts to lend the gold to traders and kings, and it was named crediting. The banker receives a payment that got the name “interest”. It was not easy to carry borrowed gold with oneself, so credits began being issued with the help of same banknotes, which the banker — please note! — just draws.

That was how modern bank credit was born — actually, a credit is an unsecured banker's liability that the latter just draws on a piece of paper.

Partially secured banknotes started to circulate as money.

This business happened to be very profitable, and the state grasped the idea and swiftly monopolized it. Shortly after that, when all banknotes almost lost all previous connection to the gold that secured them, the state “forgave” all citizens their gold, and stopped converting banknotes into gold. The money wasn't then secured by gold.

Totally unsecured banknotes started to circulate as money.

There came the Internet. There came the WebMoney and created a user-friendly mechanism of accounting property rights. The WebMoney started to accept totally unsecured debt liabilities of different countries, which are impossible to use in the virtual world, and started to give instead of them its own liabilities, which are very convenient to use in the virtual world.

Property rights in electronic form secured by unsecured state banknotes started to circulate as money.

Why did I write this long, boring reasoning? Well, it's wise to pay attention to the evolution of money (key moments are aptly marked in bold) and see that during the human history various things were used as money: Bison's hoofs, gold, notes secured by gold, notes secured by nothing, notes confirming receipt of other notes that are secured by nothing, etc.

Anything can be used as money if it has properties of money: ability to transfer, division, value, authenticity, uniqueness, measurability, equivalence, liquidity.

Money (liabilities of third persons) ARE NOT brought in, money is liabilities of participants towards each other that are GENERATED by participants themselves. When someone asks me to help move things from one place to another, we both understand that I'm going to render him a service that has inherent value and costs money, and which sometime in the future should be paid. But I don't request a $100 bail to secure his future compensating.

I TRUST him.