The camera has a motorized varifocal lens installed on it. Instead of the lens having adjustment rings and set screws, there are motors that electronically control the adjustments. Using the control (physical, via menu, etc.), you can then manipulate the zoom factor of the camera. Then, there is another motor that allows fine control of the lens or imager focus (front or back focus). This allows you to easily make changes with the dome still on. Prevents needing to roll a truck to make changes.
Many cameras now have a simple or one touch focus, where the camera finds the perfect focus, esp. important for megapixel cameras. This prevents the focus from shifting when you put the cover on.
Vandal cameras which may be impacted can make use of motorized lenses to prevent rolling a truck if the impact changes the focus.
(I'll try to post a video shortly showing the operations via web browser for an IP camera with remote focus & zoom controls).