What is txn id on bank statement?

Excuse me, could you please clarify what you mean by "txn id" on a bank statement? Is it a specific code or identifier that is used to track or identify a particular transaction? If so, could you elaborate on its purpose and how it's used in the banking system? Additionally, would it be possible for you to provide an example of how a txn id might appear on a typical bank statement, and what information it might contain? Thank you in advance for your help.