The price of any product is a determinant of the demand for that product. The Law of Demand holds that quantity demanded and price are negatively related, which is why demand curves have a negative slope in the graph. Also, because the axes of a demand and supply graph are price and quantity, a change in price causes a movement along a demand curve. A consumer's level of income also determines what and how much they purchase. However, the precise relationship between income and demand depends upon the type of product in question.
Most goods are normal goods.
Changes in income cause a demand curve to shift. For inferior goods, this relationship is just the reverse. Move the slider in Figure 3 to experience rightward and leftward shifts in demand. The price of other goods also affects the demand for products. Like income, this relationship depends on the goods in question, and a change in the price of a related good also causes a shift in demand.