The mystery of an IBAN has been around for a while. When you request a withdrawal through bank transfer, you will in some cases, dependent on your banks country of origin, need to enter your IBAN and SWIFT/BIC.
IBAN is an abbreviation for International Bank Account Number which you need if you are transferring/receiving a transaction to/from a foreign bank. IBAN usually starts with a country code (example: NO or GB) and ends with your account number. There are a few sites where you are able to calculate your codes, try typing in Google IBAN calculator or else you can contact your bank and they should be able to help.