Confirmation
Plain English
How many blocks have been added after your transaction block. More confirmations = more secure. Like layers of concrete poured on top - the more layers, the harder it is to change. Solana transactions typically confirm in 400 milliseconds (under 1 second).
Technical
The number of blocks added to the chain after the block containing a transaction. Each additional block increases difficulty of reversal through reorganization. On Proof of Work chains, 6 confirmations is standard. Solana achieves probabilistic finality in ~400ms and absolute finality after 32 blocks (~13 seconds) through optimistic confirmation and Tower BFT voting.