The tool helps you setting the MODELING AXIS, when using a selection, the move, the scale or the rotate tool.
Using C4D's native sliders is not the fastest solution, if you just go for the extremes or if you want to reset the modeling axis.
With this tool: Just click to change the axis while using the z-center of your selected components. Shift-Click to use the z-back, Alt-Click to use the z-front.
Just try it!