Bollinger Bands plot a moving average in the middle with an upper and lower band set a number of standard deviations away. Because standard deviation measures volatility, the bands widen when the market gets volatile and contract when it calms - giving you a visual read on the volatility regime.

What the width tells you

Band width is the useful part. Wide bands mean high volatility; narrow bands mean the market has gone quiet. A prolonged narrowing - the "squeeze" - signals compressed volatility that often precedes a larger move (though it does not tell you the direction). It is a heads-up that energy is building, not a buy or sell.

The touch-the-band trap

The classic mistake: assuming price touching the upper band means "sell" and the lower band means "buy." In a strong trend, price can ride the upper band for a long stretch while climbing - the same trap as an RSI overbought reading. Band touches are mean-reversion hints only in range-bound conditions, not in trends.

A touch of the band is not a reversal signal. In a trend, it is just price walking the wall.

Reading them honestly

Bollinger Bands are best as a volatility gauge and a context tool, not a trigger. The squeeze flags compression; the width frames how much room a move has; the middle line is a dynamic average. Pair them with structure and a defined exit, and they help you understand the environment - which is worth more than any single "signal" they seem to give.