ATR (Average True Range)
A volatility measure - average pip range of the last N candles. 14-period is the standard.
Useful for setting stop distances relative to actual market noise, not arbitrary round numbers. A 1x ATR stop on 1H gives room to breathe through normal wiggles; 0.5x ATR gets wicked out on every session open.
Related
Learn to actually use ATR.
Definitions are the easy part. The free first five modules put this on a real chart and make you do the work. No card required.