If price elasticity is equal to 1, then

Elasticity is an economic measure of how sensitive an economic factor is to another, for example, changes in price to supply or demand, or changes in demand to changes in income. 
Price elasticity of demand is an economic measurement of how the quantity demanded of a good will be affected by changes in its price. In other words, it’s a way to figure out the responsiveness of consumers to fluctuations in price.