Increase in Demand

Here is a figure to illustrate an increase in demand. The demand curve shifts from D₁ to D₂. With the new demand curve, there is a greater quantity demanded at every price. That is what we mean by an increase in demand.

Figure 6a: Increase in Demand

Of course, only one of these demand curves exists at any one time. Here's an animation that gives a more dynamic idea of what economists have in mind by "a change in demand."

The Animation