Sell Stop Order
A basic Sell Stop order works like this: EUO etf is trading at $21.83. You are long, and if it drops to $21.49 you want to be out. You place a Sell Stop to trigger at $21.49. If the stock hits $21.49 (either actually making a trade at that price, or being offered at that price) your stop is considered triggered. Your brokerage then immediately issues a “sell at the market” order. This may very well get you filled at $21.49 in a liquid etf, but might mean you don’t get filled until $21.40 or $21.30 in a less liquid one.