thanks a lot.....but could someone also give a sort of grammar ruling or explanation on the difference of use?
'Under' tends to mean underneath, in the sense of one thing being covered by another.
'Below' can be used to express a more vertical relationship: His name was below mine on the list. The first name does not literally cover the second name, but is in a lower position.
There are, of course, many idiomatic uses of the two words that are harder to categorize.