Your question is a bit unclear, are you interested to know how the two elements work?  In any case here is a good site that explains how an offset printing machine works.  

I also hope this segment helps:

An offset printing press is provided with a novel dual form planetary inker having improved printing characteristics. In use, a plate cylinder rotates to initially contact an ink/water form roller and subsequently contact a second form roller which is devoted exclusively to ink. The ink form roller is operable to insure that voids caused by lint, dust and other debris in the ink train are covered by the second form roller; additionally, the ink form roller provides a second working nip through which a second layer of ink is averaged with the previously deposited ink layer, such that ghosting is substantially eliminated. Both of the form rollers as well as numerous distributor rollers are rotatably carried by a shiftable frame which is pivotally interconnected with a support that carries the plate cylinder. The frame is shiftable from a first position wherein the forms are in rolling engagement with the plate cylinder and a second position wherein both of the forms are spaced from the plate cylinder; however, as the frame is lowered toward its first or working position, the ink/water form is disposed to contact the plate cylinder before the ink form, such that the plate is effectively dampened before ink is applied thereto. In particularly preferred forms, the planetary inker engages the plate cylinder on only two lines of contact, such that any one of a number of various plate cylinder diameters may be utilized.