Preview Material
Here you can select how you would like to preview the Smoothing Groups.
You can select between Flat Colors, Shaded Colors, Glossy Material and Flat Color to see how the surfaces look.
Material Setup
Here you can setup the Flat Material parameters such as Color, Secularity and Glossiness.
These settings are used for as long as you keep PolySmoother opened. If you want to make them the Default values, you can modify them from the Settings menu.