It enables you to control your camera using a cable connected to the LANC port rather than using the buttons on the camera. This can make operation much more convenient and flexible for you enabling you to focus on the shot you are trying to capture rather than the mechanics of the equipment. Basically, it lets you better control the pan bar mounted on the video head better. It also opens up the possibility of having a second pan bar which can be very useful out on location.
Additional features include maximum-speed zoom potentiometer, stand-by push button, RET push buttons (playback latest five seconds), rec/zoom/focus indicator LEDs, zoom and focus direction knob (by software), multi-speed zoom and focus knob and a focus/zoom switch.