The movement along the same curve is a change in quantity demanded. This means that there has been a change in the quantity of a good or service that consumers are willing and able to buy due to a change in the price of that good or service, assuming all other factors remain constant. It is important to note that this is not the same as a shift in demand, which would involve a change in one or more of the other determinants of demand (such as income, tastes and preferences, price of related goods, etc.).