I have no idea what you would use that mouse for I'm use to doring original design. ;D
Its used for solid modeling for programs like solidworks, CATIA, Inventor, Pro-E, ect. Its a way to rotate the models on the screen and change views. If you get into serious design work or do alot of CAD and CAM work, one of these things is a must have.
Also, if you ever used google earth, you can fly through the maps, zoom in and out and rotate without ever clicking a button. You just need to twist your left hand.