A bank identifier code, also known as a BIC or SWIFT code, is like a name tag for a bank. Just like you have a name that tells people who you are, a bank has a BIC that tells other banks who they are.
When you want to send money from your bank account to someone else's bank account, your bank needs to know where to send the money. They use the BIC of the other person's bank to make sure the money goes to the right place.
The BIC is made up of letters and numbers that are unique to each bank. It's kind of like a secret code that only banks can understand. So, when your bank sees the BIC of the other person's bank, they know exactly where to send the money.
Without bank identifier codes, it would be very difficult for banks to send money to each other. Just like you need a name to find someone, banks need BICs to find each other and send money from one account to another.