One of the more confusing topics in economics is the difference between consumer demand and the quantity demanded. Consumer demand is the entire schedule for the demand of a good for all consumers at every price, typically represented by a downwards sloping line. Changes in consumer demand are represented by shifts in the demand curve to the right (more demand) or to the left (less demand). Most of our focus in economics is on what causes shifts in consumer demand. In contrast, the quantity demanded is how much of a good is demanded given the market price; when the price changes, the quantity demanded changes. Changes in the quantity demanded are just reflective of changes in price and represent moving along a give demand curve.
Pick something that you are familiar with (e.g., motorcycles) and describe what changes in the general economy, technology, or public perception would cause a shift in consumer demand for that good. Do not talk about changes in prices for that good because that would simply change the quantity demanded.