Bollinger Bands are a technical analysis tool defined by a simple moving average (SMA) in the middle, upper and lower bands. Bollinger bands will automatically adjust to widen during volatile market periods and narrow during less volatile market periods.
Bollinger Bands are a popular indicator. The more the price moves to the upper band of the Bollinger bands, the more overbought the stock market is, and the more the price moves to the lower band, the more oversold the market is.
Bollinger Bands (BB) is not a standalone trading system. They are simply an indicator designed to provide traders with information regarding price movements.