What is unitary price elasticity of demand?

Price elasticity of demand (PED) is the responsiveness of quantity demanded to a change in price. Effectively, how much will people increase/decrease the quantity they buy of a good relative to the amount producer raises/lowers the price. This is given by the formula %Qd/%Price. A value of between 0 and -1 will be inelastic, <-1 will be elastic but a value of -1 is said to be unitary elastic. This means that the percentage increase/decrease in price will be exactly equal to the decrease/increase in quantity demanded.