What does confirmation mean?
When a block is created all the transactions that have occurred since the last block was formed are added to that block. These transactions are then considered confirmed.
While some services allow just one confirmation to serve, in reality it takes 6 confirmations, or roughly 1 hour, to be nearly certain a transaction won’t be reversed or is secure enough.
Extremely large transactions of more than $1 million might want as many as 60 confirmations to be completely secure.