As any bank usually has more than one branch in the same city or country, they use an identification code to determine the location of the branch, as well as its serial number. Basically, it consists of five digits and contains the country code and the bank branch reference number.
A bank code is a unique identifier assigned by the country's central bank (or other regulatory authority) to a licensed bank or financial institution.
In order to find a branch code and bank code, the safest way is to ask the recipient bank or consult their official websites. Fill these data in your betting account, and they will be saved automatically, so you don't have to re-enter them.