What does this formula mean? vLookup

Have you given a look to Excel's Help menu ?

,5 = fifth column of the data table once found the corresponding to A2
,0 = False or exact

Go to the Help menu < ? > and search for VLOOKUP , you will find more explanation and examples.
Else, copy the formula into a cell then click on the <fx> button on the top bar. In the pop-up click inside the cells.

It is indeed for asking questions, no worries.
The first argument is the single input value you want to lookup
The second value is the range where the leftmost column is where you expect to find the input value and usually the rightmost is where you find your result
The third argument is the column number in the above range where you will find the result. For instance, that 5 of yours indicate that you want the result 5 columns to the right of the leftmost column (counting the leftmost as 1).
The last argument is usually a zero or FALSE. It indicates that you want an exact match and not a "largest value smaller than...".

Internet is full of VLOOKUP explanations like this one: http://www.howtogeek.com/howto/13780...okup-in-excel/

=VLOOKUP(A2,'[All emploiyee reports 11 Nov.xlsx]Sheet1'!$A:$E,5,0):
Take the value in cell A2 of this sheet and look down column A of sheet1 in workbook All..Nov.xlsx then go across 5 columns and return the value in that cell.