What does a demand curve illustrate? products that are most in demand differences in price charged by different stores quantities demanded at each price by consumers differences in demand for different products?

A demand curve of a particular product is a graph that has on the y-axis the demand of that product and on the x-axis its price. It is an important concept because if the price of a product drops, one will prefer that product over other alternatives that have become now more expensive or one can buy simply larger quantities of that product; thus the consumer demand for that product increases. Similarly, if the price goes up, the demand will drop if all other things are equal (the state of economy does not change, a new competitor product does not appear etc.). Thus, by definition, a demand curve illustrates store quantities demanded at each price by consumers.