It makes you stop and look at the photograph. It plays on your emotions. It produces a definite response. Photo editors want images that make powerful statements. Anyone with an automatic camera can shoot a properly exposed scene.
Photo editors can easily tell if a photograph has impact by the way people respond to it.
The response can be positive or negative. But, it can't be one of indifference. If I feel an emotional tug, I'll sometimes display the image to others on the editorial staff and observe their reactions. In fact, I'll usually show the photograph up to a half a dozen different people before I make a final determination on the impact value of the image. An excellent way to get an honest critique is to display your photograph to members of a local camera club or to a instructor at a local college or art school.