supply and demand determines prices levels for goods and services in a market economy.
A market economy is characterized by the free entry and exit of firms, that is, it is an economic system based on competition. In this context, firms compete for the market through price practices. Consumers will buy from the firms that practice the lowest price and firms that charge a higher price will be eliminated by the competition.
When the market places a price where the supply of goods and services will equal the demand for goods and services, the economy will be in equilibrium.