bitcoin core – Why do I have multiple payment addresses associated with my private key?

About output dumpwalletThis is the best answer.

dumpwallet output documentation and description?

About your question:

Why does my private key address correspond to two payment addresses?

The address is the instructions sent from your wallet to your payment wallet.

These instructions are divided into two parts: prefixes and some strings.

If the prefix is:

• “1” means you want to lock incoming coins in your wallet. P2PKH Script (pays for public key hash) and hash your public key This is the string portion of the address.
• “3” means you want your wallet to keep incoming coins locked. P2SH Script (Pay To Script Hash) and Hash script This is the string portion of the address.
• “bc1q” means your wallet will receive the coins Segwit Scripts and Hashes script This is the string portion of the address.
• “bc1p” means you want your wallet to lock incoming coins. taproot Scripts and Hashes script This is the string portion of the address.

So the same private key can originate from four different addresses.

In the 1.txt file, the receiving address starting with 3 is followed by 00… This code should not be the private key. What is that?

This is the P2SH address of the corresponding private key.