Updated by Andrew Hall
Before a blockchain transaction fully completes, it must undergo a number of confirmations to both validate the transaction and protect against double spending. As there are hundreds of different blockchains out there, each one has its very own unique block time or the amount of time it takes for miners to discover the subsequent block.
For example, the Bitcoin blockchain averages around a 10 minutes per block whereas Ethereum's blockchain is right around 15 seconds per block. As a result, the number of confirmations and time for a transaction to complete will vary as well.
For transactions, we require 15 block confirmations. Under the 'YOUR TRANSACTIONS' tab on the bottom of the exchange, you can track the number of confirmations left by hovering over the transaction. If you wish to see the full details of your transaction on myetherscan, click on the yellow circle under the 'DETAIL' tab.