Roughly every ten minutes, a new block is created and added to the blockchain through the mining process. This block verifies and records any new transactions. The transactions are then said to have been confirmed by the Bitcoin network.
For example, if Sean sends one bitcoin to John, this transaction will remain “unconfirmed” until the next block is created. Once that block is created and the new transaction is verified and included in that block, the transaction will have one confirmation. Approximately every ten minutes thereafter, a new block is created and the transaction is reconfirmed by the Bitcoin network. While some services are instant or only require one confirmation, many Bitcoin companies will require more as each confirmation greatly decreases the likelihood of a payment being reversed. It is common for six confirmations to be required which takes about an hour.