This setting will allow a user to view only a small portion of the protein at a time, dragging the selected representation along the length of the backbone using the middle mouse button. If the user doesn't have a middle mouse button they can switch mouse modes and accomodate accordingly. Use the PyMOL help manual to discern new control schemes.
There are four preset roving views excluding the electron density roving settings. These include roving sticks, roving lines, roving ball and stick, and roving spheres. The importance of this viewing method resides in the ability to discard with the background clutter of residues in the protein concentrating on only the portion of interest. A slider is also associated with these roving views allowing a user to control how large a portion of the protein is demonstrated as the chosen representation at a time. Moving the slider to the left will reduce the amount shown. After altering the slider the user must re-click on the roving representation of choice to enact the change.