The ViewCube is a 3D navigation tool that appears when the 3D graphics system is enabled and allows you to switch between standard and isometric views.
Once the ViewCube is displayed, it displays in one of the corners of the drawing window over the model in an inactive state. When you position the cursor over the ViewCube, it becomes active. You can switch to one of the available preset views, roll the current view, or change to the Home view of the model.
ViewCube is also displayed in the Object Viewers. The ViewCube is always turned on in Object Viewers.