The purpose of Bollinger Bands is to provide a relative definition of high and low. By definition prices are high at the upper band and low at the lower band. This definition can aid in rigorous pattern recognition and is useful in comparing price action to the action of indicators to arrive at systematic trading decisions.
Bollinger Bands 101
Thanks to John Bollinger, traders were equipped with an indicator which tells them if the market is quiet or loud. With two simple bands that narrows and spreads apart when there is action.
So how does it work? When one band is pierced, price has a tendency to move to the other band. Most people think that when a candle pierces a band, it signals a change in price automatically. That’s a big mistake. This usually happens after that section or wave of the trend is done. But other conditions must apply. Remember that the use of Bollinger Bands must be in context with other indicators such as Moving Averages or the Elliott Wave pattern.