The Linear Regression indicator visualizes the general price trend of a specific part of the chart based on the Linear Regression calculation. The central line of the indicator is the linear regression calculation itself, and the lines above or below it are X number of standard deviations removed from the main one. This is a good tool to use to determine when a price is unusually far away from its baseline.
This differs from the built-in Linear Regression indicator by adding in more standard deviations to show more potential reversal points.