Bollinger Bands are a technical trading tool created by John Bollinger in the early 1980s. They arose from the need for adaptive trading bands and the observation that volatility was dynamic, not static as was widely believed at the time.
Bollinger Bands can be applied in all the financial markets including equities, forex, commodities, and futures. Bollinger Bands can be used in most time frames, from very short-term periods, to hourly, daily, weekly or monthly.
Bollinger Bands answer a question: Are prices high or low on a relative basis? By definition price is high at the upper band and price is low at the lower band. That bit of information is incredibly valuable. It is even more powerful if combined with other tools such as other indicators for confirmation.