With some types of investment, such as cash and CDs (certificates of deposit), the value of the investment is fixed. However, inflation will cause the purchasing power of this value to decrease.
With other types of investment, such as stocks and real estate, the value is not fixed. It will vary. In the short term it may even fall below the purchase price. However, over the long term, the value of the stocks and real estate should certainly increase by more than the rate of inflation.