Bollinger Bands
Volatility bands around a moving average that expand and contract with market turbulence.
Bollinger Bands plot a moving average with an upper and lower band set a number of standard deviations away. The bands widen when volatility rises and contract when it falls, so they visualize turbulence as much as price level.
A tight “squeeze” (narrow bands) often precedes a big move as volatility compresses before expanding — a watched setup. Price touching a band is sometimes read as overextension, though in trends price can “ride” a band for extended periods, so touches are not reversal signals on their own. Like most technical tools, Bollinger Bands describe volatility conditions usefully but require confirmation before acting.