Card Security Code
The card security code (CSC) is usually a 3 - or 4 - digit number, which
is not part of the credit card number. The CSC is typically printed
on the back of a credit card (usually in the signature
field).
On some cards, all or part of the card number appears
before the CSC, for example, 1234 567. In this example, 1234 are the
last four digits of the credit card number, and 567 is the
CSC.
The
number appears only on the card itself (not on receipts or
statements), so provides some assurance that the physical card is in
the possession of the buyer.