BTC Txids and private keys are related in the sense that a private key can be used to create a digital signature that confirms the owner of a particular Bitcoin address, which is then stored as part of the transaction data in the Txid.

When a Bitcoin transaction is initiated, a digital signature is created using the private key of the sender to validate the transaction and verify ownership of the Bitcoin funds being sent. This digital signature is then stored as part of the transaction data, which includes information such as the sender's Bitcoin address, the amount of BTC being sent, the recipient's Bitcoin address, and more.

Once the transaction is broadcast to the Bitcoin network and validated by miners, the transaction becomes a permanent part of the blockchain, with its own unique Txid that is generated using a cryptographic hash function. This Txid acts as a unique identifier for the transaction, allowing it to be tracked and verified on the Bitcoin network.

Overall, private keys and Txids are both critical components of the Bitcoin ecosystem, securing transactions and ensuring that Bitcoin funds can be sent and received securely and efficiently.