Since the people started to function on our planet, they have quickly observed that it is almost impossible to reach everything on their own. We have fast discovered that we need to work with each other, because of the fact that somebody has something in too big amounts and others too little. Hence, many decades ago the trade began. The most important fact related to it is to develop goods, or goods for money in such relation that will satisfy both sides. Consequently, it is impossible to force a partner in a trade to accept such conditions that will be unacceptable for him.