If there is a shift in the demand curve for DVDs, the curve can shift either to the right or to the left. The direction in which it shifts will be determined by the sort of change that occurs in the demand for the DVDs.
A demand curve has a vertical axis showing the price of the good or service and a horizontal axis showing the quantity that is demanded. This means that any demand curve shows us the quantity of the product that people can and will buy at any given price. A shift in the curve occurs when people come to be willing to buy more or fewer of a product at a given price.
In the case of DVDs, let us imagine that the cost of downloading movies from the internet drops. Now, people will not want to buy as many physical DVDs. This means demand will drop. A drop in demand is represented by a movement of the curve to the left because this shows a lower quantity demanded at each price level. By contrast, if the cost of DVD players drops, people will buy more players and therefore want more DVDs. This will cause a movement of the curve to the right.