Introduction to principles of microeconomics/Demand

The demand curve
The demand curve shows the relationship between the price of a good and the quantity demanded at each price. The demand curve is negatively sloped because of the inverse relationship between price and quantity demanded. For example, assuming that the ceteris paribus condition applies, i.e., all other factors affecting demand remain unchanged, if the price of an iPhone drops, what do you think will happen to the demand for the iPhone? Conversely, if the price increases, would more people be buying the iPhone or less.

Changes in demand
Pay special attention to movement along the curve versus shifts of the curve. The former refers to changes in the quantity demanded due to price changes. The latter refers to the breakdown of the ceteris paribus condition. In order to understand shifts in demand curve, you need to know that price remains constant and the shift of the demand curve is in response to changes in other factors that affect demand, including changes in the prices of related goods, changes in income, changes in tastes, and changes in expectations.

The resulting effect is that a rightward shift of the curve indicates an increase in demand and signifies that at any given price, consumers demand a larger quantity of the good than before, while a decrease in demandrefers to a leftward shift of the curve and signifies that at any given price, consumers demand a smaller quantity of the good than before.