Codes for transactions in nodes (or blockchains in general) are made with eth_gettransactionreceipt. You can read more about it here if you want to understand it in detail. It's a script to return the retrieval of a transaction by the transaction hash. And to tell you in more detail, a transaction receipt is the result of a user's interaction with the Ethereum blockchain . It shows both standardized information about what happened (status, txn hash, contract address, etc.) and user information about the events generated in the smart contract. In any case, my information is not enough for you to understand everything immediately and quickly. Read about it on the Internet and it will make more sense to you.