The Bollinger Bands indicator is an oscillator meaning that it operates between or within a set range of numbers or parameters. As previously mentioned, the standard parameters for Bollinger Bands are a 20 day period with standard deviations 2 steps away from price above and below the SMA line. Essentially Bollinger Bands are a way to measure and visualize volatility. As volatility increases, the wider the bands become. Likewise, as volatility decreases, the gap between bands narrows. What is done with this information is up to the trader but there are a few different patterns that one should look for when using Bollinger Bands.