The Order Book is a list of open buy and sell orders between traders. You can buy and sell bitcoins at these prices. 

Once filled, all trades on the Order Book are instant.

To buy or sell bitcoin on the Order Book, follow these simple steps:

1. Login to your account
2. Click 'Open Order Book'
3. Select 'Spot' or 'Limit' Order
4. Enter BTC Amount to buy or sell
5. Place your order!