Price elasticity is a measure of the customer reaction to price changes. For example, if you raise prices by 10% and unit sales drop 3% as a result, the demand for your product is considered inelastic. It also means that you will have higher total revenue and higher revenue per unit.
On the other hand, if you raise prices by 10% and unit sales drop 12%, the demand for your product is considered elastic. This means that you will have lower total revenue but still have higher revenue per unit.
Differing products will have different price elasticities depending on many factors including competition, perception of the product, etc. Understanding price elasticity is an important consideration in setting your prices.