Due to different technology of Monitor and Printing, it is not easy to obtain the same image color on them. Generally the contrast and brightness of monitor are much better than printing therefore photo adjestment is required and needed to decrease difference. In most case dark side of photo is clearly viewed on monitor which coldn't get same performance on printing.
EXAMPLE ▼LEFT is same picture in monitor ▼RIGHT is same picture in printing
(MORE....Difference between Mornitor and Printing)