What is TXN in PayPal?

Can you clarify what TXN stands for in the context of PayPal transactions? I'm assuming it's related to some kind of transaction identifier or code, but I'd like to understand its specific meaning and purpose within the PayPal system. Is it a unique identifier for each transaction, or does it serve a different purpose? Additionally, how can a user find the TXN for a specific transaction in their PayPal account?