In a dual clutch transmission (DCT) there are two clutches: one for gears 1, 3, 5, 7 and one for 2, 4, 6, 8. When it shifts, one clutch opens and the other one immediately grabs the next gear. In a traditional transmission, to shift the single clutch has to open and the gears move into place for the shift change. It takes longer.
This is why a manual transmission cannot beat a DCT in acceleration.