A confirmation means that there is a consensus on the network that the bitcoin transferred haven't been sent to anyone else than intended receiver and are considered his property. Once the transaction has been included in one block, it will continue to be buried under every block after it. Each of these blocks built over the one with observed transaction is another confirmation.
3 confirmations from the Bitcoin network take approximately 30 min - 1 hour and are used to avoid fraud and ensure transaction non-repudiability.
Every user is free to determine at what point they consider a transaction confirmed. For the safety of all Coinfloor users funds, we choose 6 confirmations that is considered to be as safe as waiting 3 months on a credit card transaction.