Bollinger Bands are similar in comparison to moving average envelopes. Bollinger Bands are calculated using standard deviations instead of shifting bands by a fixed percentage.
Bollinger Bands (as with most bands) can be imposed over an actual price or another indicator.
When prices raise above the upper band or fall below the lower band, a change in direction may occur when the price penetrates the band after a small reversal from the opposite direction.
int Standard Deviations
int Moving Average Type