It operates the viewpoint on 3D screen.
You can reset a view by View header > [Disp] > [View panel] if you miss where the view displays.
It scales a view by 
dragging up or down.
You can zoom in by 
dragging a mouse with pressing both the right and the left buttons on 3D image without selecting this command at default setting.
It moves the viewpoint.
If you use 3 button mouse, you can move by 
dragging a mouse with pressing the middle button on 3D image without selecting this command at default setting.
It rotates the viewpoint.
The center of rotation changes according to Center of rotation in Configuration.
You can set up in Configuration when you want to rotate 360 degrees up and down freely. And you can also change the type of rotation like a trackball in the configuration.
You can rotate by 
dragging a mouse with pressing the right button on 3D image without selecting this command at default setting.