How does a dual-clutch transmission (DCT) work and what are its benefits?

A DCT uses two clutches, one for odd gears and one for even gears, with two separate input shafts. While one gear is engaged, the next gear is pre-selected on the other clutch, enabling near-instantaneous shifts by simply releasing one clutch while engaging the other. Benefits include faster shift times (20-50ms) than conventional automatics, higher efficiency than torque converter automatics, and sporty driving characteristics. Drawbacks include complexity, cost, and sometimes rough low-speed maneuvers.