An anilox roll is a hard cylinder whose surface contains millions of very fine dimples (cells). The roll is immersed in a bath of ink and a 'doctor blade' is used to scrape excess ink from the roll surface leaving just the measured amount of ink in the cells. The roll then rotates to contact the flexo plate which receives the ink from the cells for transfer to the print material.
Anilox rolls were originally made using a diamond pecking machine, but modern rolls are laser engraved.