the quantity of a good or service that consumers are willing and able to purchase at a given price in a given time period (effective demand)
Watch these videos from mjmfoodie introducing demand
The law of demand states that an increase in price leads to a decrease in quantity demanded (or contraction of demand), ceteris paribus (Latin for "all other things remain the same", i.e. only price changes) ... and vice versa.
This next video distinguishes between change in quantity demanded (movements along the existing demand curve) and change in demand (shift of the curve to the left or right)
the quantity of a good or service that producers are willing and able to produce at a given price in a given time period
Watch this video from mjmfoodie introducing supply
The law of supply states that an increase in price leads to a increase in quantity supplied (or expansion of supply), ceteris
paribus ... and vice versa.
HL students need to be able to use linear demand and supply functions to calculate/illustrate equilibrium... click the link for some videos on how to do this