Vlookup looks for the value of one cell in the left-most column of a table. Then,
counts how many columns away from that value your data is to display in the
current cell. Here's a small example (hope it lines up right):
Sheet 1
A B C
1 Name Occupation Salary
2 Tom Engineer $60,000
3 Dick Carpenter $50,000
Sheet 2
if you want to know how much Tom makes, put Tom's name in a cell (Say A1) then use
this formula:
=vlookup( A1, 'Sheet 1'!$A$1:$C$3,3,False)
The formula looks for the value of A1 in the defined array, counts over three
columns (including the one the found value was in) and with "False", looks only
for an exact match.
HLookup works the same way except that it looks in the top-most row of a table and
counts down rows.
Hope this helps.
Rita