Dear Mr. Indrajit,
Its really very simple. Under stand the following points step by step.
1. 2 Sheets should have at least one common column let us say connector column based on which you would like to connect.
2. Comming to VLOOKUP, it has 4 parameters.
a. First parameter - is the cell value on destination sheet based on which you would like to connect.
b. Second - is the range from souse sheet (the left most column should be same as the first paramater) something like $A$1:$D$20.
c. Third parameter - is the number of that column which you would like to refer based on connector column. If A column in source sheet is starting of the range (second parameter) then B column can be referred with 2, C column with 3 and D column with 4 as third parameter.
d. Fourth parameter is a boolean value meaning either false of true. "False" stands for exact match in both the cells of 2 sheets where as "True" stands for approximate value match.
Please find enclosed file which has a simple example based on above points.
Hope this helps.
Dayal Saran M