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Stop Market
Stop orders are submitted on the opposite side of the market than normal Limit orders. A buy stop order is submitted at a price higher than the current best bid but does not fill until that price trades. A sell stop order is submitted at a price lower than the current best offer price.
Note that if the market is moving rapidly you may get filled at a worse price than the one you entered. If you want to prevent this by setting a limit price for the stop then you can do so with the Order Ticket.
Stops are useful as loss limits as you can use them to close out a position automatically if the market goes against you.