IBANs are used by banks of other member or joining countries of the European Union, the European Economic Area, Switzerland as well as a few others. A list of all IBAN compliant countries is available.
Using the IBAN is an internationally agreed method for transactions between banks located in different countries. It provides a simple means for foreign banks to check the validity of your bank account number.
An IBAN is always used in conjunction with your BIC (Bank Identifier Code).