There is a supply and a demand for most goods. The result is a market clearing equilibrium price. Companies many times (especially around Christmas) supply a certain amount of the "hot/must have" product to the market. Invariably there is more demand than supply.
A good example of this will be the new iPad 3 or Halo Reach video game (wait until Christmas and see).
Why would companies limit the number of units produced? Does this invariably lead to "black markets"? How do black markets affect the supply and demand?
What determinants of supply or demand ( book calls these "shifters") might cause a change in the supply and demand curves? Explain.