diesels are split into two basic types
direct and indirect injection
direct injection have the combustion chamber bowl in the piston itself where fuel is fed for ignition (usually very noisy if mechanical but quite easy to start - and less pumping losses as the fire does not have to pump itself out of a precup in the head)
indirect injection like your CD20 uses a pre-combustion chamber where the compressed air is forced into a tornado like ball and then sprayed with fuel making it instantly combust - which then comes out the throat of the cup and chases the piston down. (good and cheap design)
the CDI you are asking is about commonrail direct injection - the common rail direct injection is just like a petrol EFI engine BUT instead of the injectors spraying into the inlet manifold - the injectors are directly on top of the piston head. The injectors themselves are piezo electric units that inject at about 5 strokes of fuel for optimum fuel effeciency and quiet operation. The biggest difference is the injection pressure, the usual IDI engine fuel injection pressure is about 120-150 bar, the common rail DI pressure is about 1500-1700 bar (developed by a hydraulic pump on the engine itself) and the injectors are fired by the ECU