Answer:
Quantity Demanded is a shift up/down a demand curve
Increase in Demand is a shift in the curve itself.
Step-by-step explanation:
There will be an increase in Quantity Demanded when price goes down. There is a Quantity Demand change when there is a price change. (QD goes up when Price goes down, QD goes down when price goes up)
An increase in demand is when one of the shifters of demand change. So for example, if number of consumers (one of the shifters) increase, the demand curve increases, and shifts right, meaning more quantity at each pricepoint.