When using VLOOKUP why is a range needed at all?

Question

I'm having difficulty learning the VLOOKUP function in spreadsheets. Maybe I'm over thinking things, or not grasping the function properly?

Here's what I understand the basic syntax for the VLOOKUP function to be: =VLOOKUP(lookup value, range containing the lookup value, the column number in the range containing the return value, Approximate match (TRUE) or Exact match (FALSE)).

I don't understand why the range is necessary for this Function to work. With the lookup value I'm already identifying which field I want to find the corresponding data for, and with the column number I'm identifying exactly which corresponding column I want the data pulled from. Why is a range needed at all?