Lets you switch between a symbolic or solid view of the model in the window. The symbolic representation displays a line-based view of the model; the solid, or rendered, representation displays a more three-dimensional view of the model. The examples below display the two graphical representation types, with the symbolic representation on the left and the solid representation on the right:
You can toggle between the two representation types only when the 3D view is active.
Select View > 3D View > Show 
to turn on and off the 3D view.
What do you want to do?