Volatility
A measure of how much price fluctuates over a given period. High volatility means both opportunity and risk; the stop distance is adjusted to it.
Volatility is measured with indicators like ATR (Average True Range); in the options market, "implied volatility" (VIX) shows expectations.
The stop and target distances of the same strategy should change with volatility: tight when volatility is low, wide when it's high. A fixed-pip stop doesn't give the same result in every regime.