In 'Normal' mouse mode the mouse is used to view the data in the 3-D window. By pressing the left mouse button and moving the mouse while the cursor is in the 3-D window, the 3-D image can be rotated. At any instant you can only control two of the three degrees of freedom of box rotations. However, by releasing and re-pressing the left mouse button you can change your "grip" on the box. With practice you will learn to control the box through a series of mouse moves, releasing and re-pressing the left button between moves.
The center button controls two very different things depending on how the mouse is moved. Holding the center button down and sliding the mouse away from yourself zooms in, making the box get bigger. Sliding the mouse towards yourself zooms out and makes the box get smaller. Holding the center button down and sliding the mouse right moves a plane of invisibility (i.e. a clipping plane) into the box, creating a cut away view of the box contents. Sliding the mouse left brings the clipping plane toward yourself, eventually out of the box altogether.
The right mouse button is pressed to translate the box in the window. This is useful if you want to zoom in to something that is not in the center of the box. Note that the center of rotation for box rotations stays at the center of the screen rather than in the center of the box.
The other five viewing modes will be discussed in detail in following sections.