This is a version of Bollinger bands made as a filled area. But to avoid just making the usual Bollinger bands with some more colors, this version has a choice of calculating the standard deviation as a sample or as an uncorrected deviation. The explanation for that would be the following.

The difference is usually not big, but it exists. So now we have the Bollinger bands with a choice of these two deviation types too (with the usual set of 22 price types addition).