Photography, just like painting, can be used either as an art or as a technic. Nowadays, painting is mostly used for art, but an example of it being used as a technic occurs when a painter paints the scene of a trial in which cameras are forbidden in the courtroom or when a wanted criminal is painted when no photograph is available. The technical function of photography is obviously to document an event, to literally capture an image that can be viewed later. People take pictures of themselves at happy occasions and browse through them later to recall their joy or put them up on Facebook as it would be a travesty if their enjoyment were not shared with the rest of the world.
Photography can be used as an art when the photograph conveys something other than just the event, person, or place it portrays. A person may be arranged and painted artistically, as that nude women in one of the photographs at MoMA was. However, a photograph may be taken of a piece of art itself to convey an additional something about that piece through the perspective in which the photograph is taken, or a photo of an element of nature can be art if a particular something is emphasized. A good rule of thumb is if the photo has a value, usually an aesthetic one, other than just as a record of an event.
Sometimes photography can be used as a technic and an art at the same time, by combining practical usefulness with aesthetic values. The line between the two is not always clearly demarcated.
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