Mathematical Description of the envelopes/volatility bands

[Tobedotty]

Hi all, I'm looking for a mathematical description of the envelopes that are included in Bet Angel's graphing interface. There are lots of different types of envelopes out there which is why I'm asking, as it is quite hard to tell just by looking at them. Thanks in advance.

[Euler]

Two standard deviations from the moving average.