Bitcoin glossary
Confirmation
Each block mined on top of your transaction — settlement depth, counted.
A transaction is “confirmed” when it is included in a block, and gains one further confirmation with every block mined after that. Each confirmation makes reversal exponentially harder, because an attacker would need to redo all that mining work faster than the honest network extends the chain.
Convention treats six confirmations (~one hour) as final for large amounts; small payments often accept one, and Lightning payments settle instantly without waiting for blocks at all.