It means something. As a reader (we mentioned photographs are read) of an image, certain assumptions are made, specifically that we as photographers know what we are doing, and that whatever is in the image, was there by choice. As a photographer, we may or may not have more difficulty in this aspect, as if an artist does not want an empty soda can on the ground near his subject, he simply does not paint one. If there is one in a photograph we create, it is assumed that it was left there, or rather, included in the image, with intent, and purpose.
*Side note. . . this is why simple images, are often so successful. There are much less elements competing for attention, and so the communication and intent is easier to convey to the reader. *

The time most pivotal for conveying our intent or vision for any image, is before the image is made. It is at this crucial moment, when we can change things, after that shutter is released and that light is exposed to the sensor/film, the scene is flattened into two dimensions, and captured in the manner we chose, whether with great intent, or just a thoughtless push of a button.

Meaning, is where Subject, Subject Matter, and Composition overlap, you may think of it as Message, Elements, and Decisions. David helps to break it down in this way. Subject, and Subject Matter are different, just as the story, is not the moral of the story. In the tortoise and the hare, the Subject is patience, the Subject matter, or the way the story is. . .

To read more, check out this [link]