Difference between GDP at current prices and real GDP?

Current price GDP measures value-added production in today's prices. Increases in current price GDP can be driven simply by price changes when one of the key pieces of information that is needed is whether or not the quantity of final goods and services available is increasing or not. For this reason GDP series' are often expressed in constant price. On the contrary to this,Constant price GDP measures value-added production expressed in the prices of a particular year, known as the base period.

It is calculated by adjusting nominal values for price changes. By expressing current price series' in constant prices we can analyse the price and volume components separately.