This property is a shader assignment UI to connect RenderMan shaders to objects or groups of objects and entirely skip the usual Render tree. The UI is accessible through the Render -> Property -> 3Delight -> RenderMan Shaders menu.
The interface will show differently depending if it's connected to a light or not:
After specifying the shader, its parameters will appear in the interface and can then be modified or animated. The Reload button is handy during shader development: it re-reads all shader parameters and rebuilds the interface appropriately. More in Using RenderMan Shaders.