Bollinger Bands are a technical analysis tool used in financial trading, including in crypto markets, to measure volatility and determine the direction of asset price trends. The tool consists of three lines drawn around the asset's price:

- Upper Band: The upper line of a Bollinger Band is the moving average value (e.g., simple or exponential moving average) of the asset price plus some standard deviation of that price. A commonly used standard deviation is twice the standard deviation of the average value.
- Middle Band: The centerline of a Bollinger Band is the moving average value of the asset's price over a period of time. This period is often the same period used to calculate the upper and lower lines.
- Lower Band: The lower line of a Bollinger Band is the moving average value of an asset's price minus some standard deviation of that price. Like the upper line, the commonly used standard deviation is twice the standard deviation of the average value.

Bollinger Bands are often used to identify overbought or oversold market conditions. When prices approach the upper line, it can indicate that the market may be overbought, while approaching the lower line can indicate oversold conditions. In addition, the width of the Bollinger Bands (the distance between the upper and lower lines) can also provide clues about market volatility.

In the crypto context, Bollinger Bands are often used in conjunction with other indicators and technical analyses to confirm trading signals and investment strategies. It is important to remember that like all technical analysis tools, Bollinger Bands are not a perfect single indicator, and need to be combined with other analyses and proper risk management.