Ummmmmmm, bit of a tricky one that Peter. Fine art is something that nowadays constantly seeks to re-define itself. The grey areas where it bleeds into other genres are also large and ill-defined. I can only really explain what fine art means to me in regards to my own photographs. This probably will not stand up as a good definition for others and their work. You will see that my explanation is on the contrary to that in the link.
I really take two kinds of photographs:
Those that are of things I like and would like a photograph of just because they will (hopefully) look good. They can be of all sorts of things and might tell a bit of a story with the subjects in them. Old buildings, shabby streets, interesting things found while walking about, scenery, animals, etc. In a sense these are all documentary in varying degrees.
Those that are based on an idea and are taken with the intent of communicating something. This could be a social comment, an observation, about how we relate to images, etc. These photographs could be of anything really, in a sense it all distills down to the intent when the photograph is taken.
However, as said before there is a large grey area potentially even between these two definitions. Though historically fine art was considered to be an artwork produced as a result of disciplined work and was judged primarily on its aesthetic qualities. These days often fine art is judged primarily on other factors, often with aesthetics at the bottom of the list.
I imagine that makes it clear as mud and crystal as the same time!