The difference between fantasy and horror

The wife and I were discussing a story I've been working on, and she brought up a question about the ending. She felt a character should have been more forceful with particular actions, whereas I disagreed with her.

Well, it's my story, so we'll see how things turn out.

However, though my story takes place in a fantasy world, it is at heart a horror tale. My wife did not understand the difference, she not being a big fan of either genre in literature, so I had to explain it to her in terms I thought she would understand.

Basically, I told her the difference between fantasy and horror was that in fantasy a big monster would show up and everyone would gather their swords and charge out to kill the beastie, whereas in horror a big monster would show up and everyone would suddenly go, "Oh shit! We're screwed!" And more than likely they would be, or at least some of them would be.

Now I admit that is a generic, extremely oversimplified explanation of a comparison between fantasy and horror. Obviously both genres are far more expansive and potentially expressive than the limits I laid down.

But I still kind of liked it.