Our eyes are about two inches apart and each eye sees a slightly different view. Our brain combines these views from our two eyes to see things in 3-D.
3-D vision helps us see depth. With it we can locate the things around us, judge how far away they are, and reach them. Without 3-D vision it’s hard to grab a book or catch a ball, but it’s not impossible. People with only one good eye can also sense depth. That’s because their brains pick up visual clues from the world around them and learns how to see 3-D.