This economy speech by Sally Blount breaks down the origin, meaning and reason for our monetary system.
Sally explains that markets were started by humans buying and selling goods. Sellers would decide they didn't want a product as much as the money offered by the seller. This would help make it possible for everyone to benefit by focusing on one thing, but benefit from a variety of different goods. This same model is still very similar today.
An important point raised by Sally's economy speech is the fact that our markets are completely amoral. It is not the markets that choose who to unfairly give wealth and benefit to, it is the people that make it immoral. If our markets were used properly they would benefit everyone more effectively.