A market order is an order to buy or sell an asset at the bid or offer price currently available in the marketplace. When you submit a market order, you have no guarantee that the order will execute at any specific price.
To create a Market order
Click the Ask price to create a BUY order, or the Bid price to create a SELL order.
In the Type field select MKT as the order type.
To transmit the order, click the "T" in the Status field.
For a more detailed description of market orders, visit the Order Typesinformation page.