What is a Bitcoin transaction ID, or TXID?

Detailed explanation

A transaction ID, or TXID, is an identifier used to name and find a Bitcoin transaction. It helps locate the same event in a wallet, node or block explorer instead of searching only by approximate time or amount.

A TXID alone is not a confirmation. A transaction may already be known but still await inclusion in a block. Checking therefore also requires seeing whether it is actually found and how many confirmations it has.

The identifier is neither a private key nor a seed phrase. Checking a payment does not require the recipient's secret recovery data. Public transaction information can, however, reveal clues about payments, so it should be shared deliberately.