An auto clutch transmission is a type of manual transmission which can be electronically switched between modes. Allowing a computer to take over, apply the clutch, and perform the job of shifting the gears, or full manual control of clutch and gear shifting by the driver. This type of transmission allows the driver to set to automatically apply the clutch while they shift, taking away much of the possibility of gear damage caused by incorrect shifting and clutch application. When in manual modes, shifting is accomplished either using steering wheel mounted paddles or a floor mounted stick shift.
.For more info, see How A Gearbox Transmission Works