There was a small village by the river. At first, there where only two families. One of them bred rabbits, and the other grew wheat. To diversify their diet, they traded with each other. They agreed that one bag of wheat will be exchangeable for one rabbit. After some time, other families began to settle on the village. Every family produced something else. Some of them produced clothes, others fished and still others bred cattle. Over time, there were many goods and services.
A shoemaker, send his daughter Catherine to get a bag od wheat. The girl took the shoes and went to the farmer to propose a trade. The farmer agreed because he needed shoes and so they exchanged. Next day, shoemaker, sent Catherine again to get another bag of wheat. But this time the farmer replied: “I’m sorry, I don’t need a second pair of shoes, but I will give you wheat for a box of apples”. So Catherine went to the gardener and proposed to exchange the shoes for some apples. The gardener replied: “I never wear shoes in the summer, I won’t be needing them for at least six months, I can give you apples in exchange for new horseshoes for my horse though”. So the girl went to the forge, but the blacksmith said, that he will give her horseshoes only for a new pair of trousers. Finally the local seamstress agreed to exchange shoes for trousers. Unfortunately, this wasn’t the end. It took Catherine half a day to find someone who needed shoes, but it took another half a day to finally get the wheat that she wanted.