A movement along a given demand curve caused by a change in demand price. The only factor that can cause a change in quantity demanded is price. A related, but distinct, concept is a change in demand.
A change in quantity demanded is a change in the specific quantity of a good that buyers are willing and able to buy. This change in quantity demanded is caused by a change in the demand price. It is illustrated by a movement along a given demand curve.
In fact, the only way to induce a change in quantity demanded is with a change in the price. Anything else, everything else, causes a change in demand.
As the demand price induces a change in the quantity demanded and a movement along the demand curve, the five demand determinants (buyers' income, buyers' preferences, other prices, buyers' expectations, and number of buyers) remain unchanged.