Developed by John Bollinger, Bollinger Bands allows users to compare volatility and relative price levels over a period time. Bollinger Bands are envelopes which surround the price bars on a chart. They are plotted two standard deviations away from a simple moving average. Because standard deviation is a measure of volatility, the bands adjust themselves to ongoing market conditions. They widen during volatile market periods and contract during less volatile periods. Bollinger Bands are, essentially, moving standard deviation bands..