Nominal refers to a measurement of GDP given current prices.  Nominal prices are therefore the prices that we observe when we go shopping, or check out products on the internet.  Real GDP refers to measuring the GDP using past prices as a base.  Using real GDP or prices allows us to make comparisons across years without worrying about the effect of inflation.  For example, if we only look at nominal GDP numbers, we would see strong growth over time.  In order to find out how much GDP really grows, we need to use a tool called the GDP deflator.

Great right?  But how do we figure this out?  We need to have nominal and real numbers