Method of focusing the lens, using either a rotating mechanical action or a motorised method, where you enter a distance on the camera. Cameras with mechanical actions often have an aid to help you focus correctly. On some cameras you see the image split in half and as you adjust focus the two halves come together. When the images are lined up the focusing is achieved. Others have an LED indicator that blinks when out of focus and either goes out or stays on when focusing is correct.