The document discusses the concept of elasticity of demand and its types. It defines elasticity of demand as the percentage change in quantity demanded given a percentage change in a determinant like price. It then explains the different types of elasticity based on the quantum of change in quantity demanded relative to the change in price - perfectly inelastic, inelastic, unitary, elastic and perfectly elastic demand. The determinants that impact price elasticity like availability of substitutes and nature of need are also outlined.