The document discusses the different types of changes in demand. It defines demand and explains the demand function. There are two types of changes in demand: (1) Extension or contraction of demand due to changes in price with other factors remaining the same, which results in movement along the demand curve. (2) Shift in demand due to changes in factors other than price with price remaining the same, resulting in the demand curve shifting up or down. An upward shift represents increasing demand while a downward shift represents decreasing demand.