When using a Stop order (STP), you only designate one price: your Stop Price. Once your Stop Price is hit, it will trigger a market order for execution. When using a Stop Limit order (STP LMT), you must designate two prices: a Stop Price and a Limit Price. Once your Stop Price is hit, it will trigger a limit order at the price you designated for execution.
Additional information on Stop orders and Stop Limit orders can be found on our website. Additional information on the the difference between a stop and a stop limit order as well as more information regarding the use of stop orders on can be found in our Knowledge Base.