when you open up say Pro tools or in my case Sonar Producer, if you have the fader for a track (in the application) set at +5db the fader (on the real life unit such as the BCF2000) will automatically move to that position. You can then control it and edit it via the fader in your hand instead of your mouse on screen.
If they aren't motorized to go into the place that the tracks volume is in the application already, you'll have to move everything around again.... make sense? easy to show but hopefully that makes sense.
Better yet, youtube some mixers such as the command 8 and the BCF2000. it may help you get a better idea to see it in action.