Photography consists of two words, the first of which—light, is the most important. From the Wikipedia:
The word comes from the Greek words φως phos (”light”), and γραφις graphis (”stylus”, “paintbrush”) or γραφη graphê, together meaning “drawing with light” or “representation by means of lines” or “drawing.”
Watching the light is most of the work in photography; observation is as much the art of photography, as recording it. After some practice, watching the light interact with surfaces, and seeing how soft or harsh it is, its hue and tone, are some of the things you become aware of. Does it create a hard shadow? Is it warm or cool? Does it evoke an emotion within you? The last question is probably the hardest— almost abstract— qualification of the meaning of light.
The subject in the photograph of course, is worth mentioning. Who or what we are recording gives meaning to the light; it becomes a partner with the color and space. Next, is the meaning and context of the photograph— what the subject has to do with the time and place, and the photographer.
Accompanying photographs together add a narrative; it gives the viewer a sense of story and further meaning. Inferences and implications start to form and provide an emotional picture, as well as a visual one. Put together, we can finally relate to a body of work, the subject, the photograph, and ultimately, the light.