The study of how the forces of supply and demand work.

Lawn Boy learns that his supply (lawn-mowing) is in great demand when many neighbors ask him to mow their lawns (chapters 1-3).

When supply exceeds demand, the price of a product will drop, and when demand exceeds supply, the price of a product will increase.

In today's economy, there is a huge demand for gasoline, but not a lot of gas (supply). That's why gas prices are so high.

a market system based on private ownership, competition, and no government interference.

The U.S. economy is built on capitalism.  For example, Microsoft and Apple are competitors in the market, competing for the most customers of technology.