The document discusses the law of demand and how demand curves illustrate the relationship between price and quantity demanded of a product. It defines elasticity of demand and explains that elastic demand means quantity demanded is very sensitive to price changes, while inelastic demand means quantity demanded does not change much even with large price changes. Several factors are presented that can impact a product's elasticity, such as availability of substitutes, importance of the product, and whether it is a necessity or luxury. The document also discusses how non-price factors can cause demand curves to shift, changing the overall quantity demanded at each price.