Fine art photographs are those that have no other purpose than to be themselves. They are not of weddings, bar/bat mitzvahs, events, news stories, real estate where the intent is to represent the property for sale, travels, or other things that need to have an image made for a reason. That said, fine art images can be about any of those things but just not for a purpose. The field is so wide open and amorphous that it might as well be thought of as indefinable in terms of what a fine art photograph 'should' or 'does' look like. Interesting anyone other than yourself in what you've pictured, however, is also as mysterious as whatever the 'fine art' photograph is. Photograph whatever interests you, and do it well. Let someone else decide for himself what it is beyond that.
There's also a lot of crossover in those genres (perhaps not real estate or wedding photos) though- look at Weegee as a prime example. His work now sells in galleries and is exhibited in museums. Same with Robert Capa. Now I doubt I'd want to hang a four-foot copy of one of the D-Day landing photos on my dining room wall, but I could see having an 8x10 print in an office somewhere. The thing I most often think of when someone says "fine art photography" is they're trying to distinguish their female nudes from cheesecake/boudoir/Playboy photography. Which is widely open to self-definition. One man's 'fine art' is another man's monkey-spanker.