This document discusses demand and supply analysis. It begins by defining demand as a want supported by both willingness and ability to pay. There are three conditions for a product to have demand: desire to buy it, willingness to pay the price, and ability to pay. Demand can be of different types depending on price, income, or related goods. The law of demand states that as price increases, quantity demanded decreases, assuming other factors remain unchanged. A demand curve on a graph shows the inverse relationship between price and quantity demanded. A change in a factor like income can cause a shift in the demand curve, representing a change in demand rather than a movement along the curve.