Bitcoin glossary
Transaction
A signed instruction spending UTXOs to new owners, recorded forever on-chain.
A Bitcoin transaction is a cryptographically signed message that consumes existing UTXOs and creates new ones assigned to the recipient’s addresses (usually including a change output back to the sender). Once buried under confirmations it is practically irreversible — there is no chargeback mechanism, by design.
Irreversibility is a feature for merchants and a responsibility for senders: verify addresses before sending, because no support line can undo a transaction.