Printed element
From Brickwiki
A printed element is any LEGO brick or other element to which a design has been applied in the manufacturing process. Printing is much preferred to the use of stickers by most fans as the design is more permanent and exactly applied by machine.
Pad Printing
A technique used to print designs on curved surfaces such as minifigure heads or curved slopes, pad printing is a mechanical process where ink is picked up and applied by a sponge-like applicator and applied to the element. In the second decade of the 21st Century this technology became common amongst vendors looking to provide printing not available on official elements.