You can select different viewing modes in which to display your scene. By default, the Wireframe view mode is displayed in each window.
If you want to modify only one view at a time, you can click the W (Wireframe), S (Shaded) or T (Textured) icons displayed on the title bar of each view.
The Wireframe mode offers the fastest display. Objects are displayed as a curve meshes.
The Shaded mode is useful to see the shape of the objects and how lights illuminate the scene.
The Textured mode displays not only the shape but also the texture and/or the procedural material assigned to objects. In case of procedural materials, which have no textures, the representation does not exactly fit the final effect being only aimed to give you an idea of what to expect. The textured mode takes the longest time for refreshing the display but it can be very useful for previewing your scene before starting the rendering session.
See also: