This command switches (toggles) the rendering mode to wireframe. When in wireframe mode all objects, including buildings will have their wireframes rendered instead of their textures.
If wireframe mode is disabled, executing the above command will enable it. If wireframe mode is enabled, executing the above command will return rendering to normal (texture rendering).
ToggleWireframe is simply a longer version (alias) of the TWF command - it has the exact same function.