Level: SL and HL. Sections marked HL only are for Higher Level students.
Demand shows how much of a good consumers are willing and able to buy at each price. It is one half of the market model that the rest of microeconomics builds on.
The law of demand states that there is an inverse relationship between the price of a good and the quantity demanded, ceteris paribus: as price rises, quantity demanded falls, and as price falls, quantity demanded rises.
'Willing and able' matters. A student may want a new laptop, but unless they can pay for it, that wish is not effective demand. Demand is also always measured over a time period, such as per week or per year.