Assuming your not , it's exactly what it sounds like , a H-H mount that is motorized will move your dish on the arc so that you can catch signals from different satellites , your avatar has 2 dishes and I can see it has a H-H mount.
Whether or not you really can go Horizon to Horizon can be debated.
I guess , other c-band people can answer better.
What type of Actuator do you use ?
Which motor type is the best and most affordable ?
What type will really let me see more of the arc ?
Why is the term flipping over used when moving a BUD to the extreme east or west ?
When I had my BUD (along time ago - so things may be different now) , the standard dish mover (arm) only went so far (which was in my case enough to get all but 1 of the sats I needed), A h-h mount will allow you to go from one side to the other (hence the name horizon to horizon), I had always wanted one but at the time they where very expensive and I was poor (well poorer )
Basically it is a type of motor that will move your dish from East Horizon / West Horizon using a DiSEqC positioner (usually built-in your DVB receiver).