What Shifts the Demand Curve?

What are the factors that cause the demand curve to shift to the left or to the right? What does it mean when demand shifts?

An increase in demand means an increase in the quantity demanded at every price. Similarly, a decrease in demand means a decrease in the quantity demanded at every price.

This video looks at real-world examples of some important demand shifters, such as changes in income (both for normal and inferior goods), population, tastes, the price of related goods (both for substitutes and complements), and expectations.