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What is a One-Cancels-the-Other Order - (OCO)

A one-cancels-the-other order (OCO) is a pair of orders stipulating that if one order executes, then the other order is automatically canceled. An OCO order combines a stop order with a limit order on an automated trading platform. When either the stop or limit price is reached and the order executed, the other order automatically gets canceled. Experienced traders use OCO orders to mitigate risk and to enter the market.

Often traders have to use two different accounts to be able to hedge against market movements. 
But with these types of orders available it is possible to setup a very secure and fast trading system that hedges your positions on one account. 

Safe trading!