During the gravure printing process the printing cylinder rotates in the ink pan where the engraved cells fill with ink. As the cylinder rotates clear of the ink pan, any excess ink is removed by the doctor blade. Further around, the cylinder is brought into contact with the substrate, which is pressed against it by the rubber covered impression roller.
The pressure of the roller, along with the capillary draw of the substrate, results in the direct transfer of ink from the cells in the printing cylinder to the surface of the substrate. As the printing roller rotates back into the ink pan, the printed area of the substrate proceeds through a dryer and onto the next printing unit, which is normally a different color or may be a varnish or coating.
Precise color to color registration (http://en.wikipedia.org/wiki/Printing_registration
) is made possible via side and length register control systems.
My old machine use worm gear to manually adjust both side and length register. For modern machine, a computer through series of sensors and stepper motor do the job which is of course yield much precise job.