Stop order
A pending order that turns into a market order when price reaches a set level. Used for breakout entries and for stop-loss.
A buy stop goes above the current price, a sell stop below it. Since it becomes a market order when triggered, it's exposed to slippage; a "stop-limit" turns into a limit order when triggered.
A stop-loss is technically a stop order in the opposite direction. If a prop firm's rules require a stop-loss, every position must have an attached stop order.