Definition
A confirmation indicates that a transaction has been included in the blockchain history a node currently accepts. In Bitcoin, inclusion in a block gives the transaction its first confirmation, and each additional block built above it increases the count. More depth usually makes replacement of that history more difficult under proof of work, but confirmations are not a mathematical guarantee that a reorganization is impossible. A transaction seen in the mempool has not yet received a confirmation, even when a wallet displays it as pending. Different recipients may require different confirmation depths depending on transaction value, risk tolerance, and operational circumstances. There is no single waiting count that makes every payment equally safe. Users should also distinguish on-chain confirmations from an exchange's internal deposit processing, which may involve additional checks before the platform credits an account.
Source references
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