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.
Yes that's what I often call my nudes to distinguish them from lame crappy nudes, and I also described them in post #22 of the above link to the other thread about fine art if anyone's curious,