There are many discussions about these 2 indicators, Polynomial Regression Channel aka PRC and Center Of Gravity aka COG.
PRC stands for Polynomial Regression Channel. This is a regression indicator that is used on charts.
A linear regression indicator draws a straight line of best fit on a chart. The PRC indicator applies a polynomial function to the linear regression function to adapt itself to the flow of market prices. Since they are regression bands that self adjust for volatility.
COG stands for Center Of Gravity and is based on the cycle work of Hurst; they are Hurst bands. Hurst’s theory was all that instruments move in a cycle and this cycle will show up in highs and lows. Prices tend to regress toward the mean, which is represented by the blue center-line. The band above and below the center-line represent the sigmas of the actual data points from the mean center-line.
Both of them are originally created for MT4 as I believe, the algorithm and code of these 2 indicators are almost identical.