A Stop order places a market order when a certain price condition is met. So it works like a limit order, in that it goes on the order books, but it buys or sells like a market order. Stop orders are therefore subject to the same fees as market orders and are subject to slippage.
You can choose to set a Stop buy or a Stop sell order, and you will have to pay a fee for your transaction; the so-called 'Taker Fee'.
As your Stop order is executed, like a Market order slippage may occur. This means that you get a slightly higher price with a Stop buy order or slightly lower price with a Stop sell order. In very volatile times, slippage can be substantial.
Example: Suppose you hold 10 Ether (ETH) in your Bullex balance and you placed a Stop sell order for the ETHEUR pair with a Stop price of 180 Euro. Once the Market price of the ETH drops below 180 Euro, your 10 ETH will be sold as soon as possible against the going Market price. If the market price drops immediately to 170 Euro, this may be the price against which your ETH is sold.
The type of trade mentioned in this example is sometimes also referred to as a "stop-loss order," as this strategy allows you to limit your losses. However, this type of order can also be used to guarantee profits. Assume for example, that you bought your ETH at 150 Euro and now the market price for ETH is 200 Euro. Placing a Stop order at 180 euro will guarantee profits of approximately 30 Euro per ETH, depending on how quickly the market order can be filled.
Please note that it is not possible to undo and/ or reverse a Stop order once it has been executed. As long as your order has not been executed, it is possible to cancel your Stop order. To cancel an open order, please visit the trading page for that specific trading pair, and scroll down. There you will find a section called 'Open orders'. Select the order you want to cancel. To the right you will see an option to click 'Cancel'.