The inclusion of a transaction in a block. A bitcoin or ethereum transaction is considered unconfirmed until it has been included in a block on the blockchain, at which point it has one confirmation. Each additional block is another confirmation.
Here are the number of confirmations that Coinbase requires to consider a transaction final for some of the assets on our platform.
Number of confirmations
Ethereum (ETH) or other ERC20 assets
Ethereum Classic (ETC)