#N/A is the output you receive in a particular formula.
The #N/A error value occurs when a value is not available to a function or formula.
However, If certain cells on your worksheet will contain data that is not yet available, enter #N/A in those cells. Formulas that refer to those cells will then return #N/A instead of attempting to calculate a value.
Also, you can override this output by different means in functions according to your requirements.