Bollinger Bands
Also called: bollinger band, volatility bands
Bollinger Bands plot a moving average with bands two standard deviations above and below, so they widen in volatile markets and contract in calm ones. Roughly 95% of price action falls inside them by construction, which means touching a band is normal rather than extreme. The squeeze — bands contracting sharply — is the most-used signal, read as compression before an expansion in volatility.