1.   Aide-memoire
Visual record for a potential memory. The photograph functions simply as a way of recalling, a way of summoning up the past.
2.   Reportage
The photograph serves as a testimony. The photographer chooses to go where most of us dare not.
3.   Work of art
The photograph presents itself as a quasi-painting, a pseudo canvas.
4.   Topography
Photograph tries to reproduce the effect of a painted landscape, etc.
5.   Erotica and pornography
Perhaps a field of photography can claim as its own. The gamut is extensive, the nuances of the erotic are manifold.
6.   Advertisement
These are photographs that are meant to function wholly as a form of allurement.
7.   Abstract image
The photograph functions simply and purely, being judges, like an abstract painting in terms of form, pattern, texture, and composition.
8.   Literature
To ‘read’ a photograph as if it were part of a narrative or a short story.
9.   Text
Photography of writing or printed signs. Something about words seems to provoke the desire to photograph them.
10. Autobiography
Every photograph, if we know enough about the circumstances of its taking, will contain some biographical information about the photographer. Will all the photographs a person takes in his/her life be as much a record of that individual as anything written down?
11. Composition
Could be argues as a sub-class of ‘work of art’ but the tradition fine art concepts and composition apply to photography.
12. Means to end/tool
The pragmatic advantage of photography. What was the photo’s initial purpose? Once the pragmatic task of the photograph has been satisfied it may transmorgify into something else.
13. Snapshot
Ties in all of the above. What distinguishes photography from all the other visual arts is its particularly intense relation to time.

-William Boyd-
Anonymous: Enigmatic Images from Unknown Photographers