What is a dual mass flywheel?

Please clarify two points for me. Exactly what is a dual mass flywheel, and is it something to be regarded as a potential future bill, like belt driven cams? Secondly, what does the term 'common rail diesel' mean, and is this an advantage?
A dual mass flywheel is a two-piece flywheel that absorbs torque, either using a system of springs between the two masses or by compound between the two masses. This absorbs vibration and reduces the torque reaction on first and second gears which can be very severe with a diesel engine. The sprung type works best and these are commonly fitted by Ford.

A common rail diesel is an engine where the fuel is pumped at high pressure into a single 'rail' and piezoelectric injectors control the flow of fuel into the individual combustion chambers.
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