1) Price elasticity measures the responsiveness of quantity demanded or supplied to a change in price. It is calculated as the percentage change in quantity divided by the percentage change in price.
2) Demand can be elastic (Ped > 1), unit elastic (Ped = 1), or inelastic (Ped < 1). Supply can also be elastic (Pes > 1), unit elastic (Pes = 1), or inelastic (Pes < 1).
3) Factors like availability of substitutes, proportion of income spent, and time elapsed impact price elasticity of demand. For supply, factor substitution possibilities and spare production capacity determine elasticity.