when i try to use vlookup formula by using another sheet then i am getting the error #NA#
Can you share an example?
It doesn't matter you VLOOKUP on the same or another sheet. Main reasons for #NA error with VLOOKUP are described here How to correct a #N/A error in the VLOOKUP function
Naming the "Table Array" makes it easier and less error prone when creating a 2 dimensional function (like the one you are talking about).
Naming is as easy as selecting the Table array and typing any name of your choice (No Spaces) in the Name Box (to the left side of the Formula Bar) followed by hitting ENTER (for the name to stick)