The DSG box is a special box which has 2 clutches in it, one of which is specifically for 'odd' gears ie 1st, 3rd, 5th and 7th, and the other clutch is for the 'even' gears, 2nd, 4th and 6th.
Basically this makes the gear changes very smooth and quick, as the next clutch is already primed and ready to engage as soon as the previous gear is disengaged.
The box can be just a standard auto box or can be used in tiptronic mode.