Nominal values refer to the unadjusted rate or current price, without taking inflation or other factors into account as opposed to real values, where adjustments are made for general price level changes over time.
Since nominal value does not adjust for the effects of inflation. This renders nominal value a bit useless when comparing values over time. It is for this reason that investors prefer real values, which factor in inflation, to give a relative comparison that is more accurate and understandable.
The famous Fisher equation captures the relationship between nominal and real value (or interest rate) under inflation:
Real value = Nominal value - Inflation rate
For example, if nominal gross domestic product (GDP) growth rate is 5.5% for a given year and the related annual inflation rate is 2%, then the real GDP growth rate for the year is 3.5%.