Final answer:
A shift in demand means that at any price level, the quantity demanded will be different. It can be caused by changes in consumer incomes, tastes and preferences, population size, prices of related goods, and expectations.
Step-by-step explanation:
A shift in demand means that at any price (and at every price), the quantity demanded will be different than it was before. For example, if there is an increase in demand, the entire demand curve would shift to the right, indicating a greater quantity demanded at every price level. On the other hand, if there is a decrease in demand, the entire demand curve would shift to the left, indicating a lower quantity demanded at every price level.
Factors that can cause a shift in demand include changes in consumer incomes, tastes and preferences, size of the population, prices of related goods, and expectations. Graphically, a shift in demand results in the new demand curve either lying to the right (increase in demand) or to the left (decrease in demand) of the original demand curve.