This control lets you switch between displaying maps as shaded (Phong) or realistic (full detail) in viewports/
The control for showing maps in viewports is a flyout with four possible states:
Show Shaded Material in Viewport [off]: Uses the Shaded style and disables viewport display of all maps for the active material.
Show Shaded Material in Viewport [on]: Uses the Shaded style and enables viewport display of all maps for the active material.
Show Realistic Material in Viewport [off]: Uses the Realistic style and disables viewport display of all maps for the active material.
Show Realistic Material in Viewport [on]: Uses the Realistic style and enables viewport display of all maps for the active material.
For details, see Viewport Display of Materials .