A fable is a short, sometimes a very short, story that conveys a moral and typically has characters which are anthropomorphized animals (or animals that have human characteristics and qualities). In "The Fox and the Grapes," a fox sees a lovely bunch of juicy-looking grapes, and his mouth begins to water. The grapes are hanging high on a branch, and so the fox tries to jump to them. He falls short of reaching the grapes, and so he takes a running leap at them; again, he falls short.

Over and over, the fox tries to reach the lovely grapes, but he can't. Next, he sits down and looks up at the grapes as though they disgust him, and he calls himself a fool for wearing himself out just to get a bunch of sour grapes that aren't very good anyway. The fox, clearly, is given the human quality of speaking as well as of rationalizing his decision-making. The lesson, or moral, that this fable conveys is the idea that we often pretend to dislike or not want something that we know is out of reach, literally and figuratively.

The fox wants the grapes until he realizes that he cannot have them, and so he decides that he doesn't want them after all and that they must not be very good. If I apply for a job that I really want and then I don't get it, I might similarly decide that the job wasn't that great anyway and that I really don't want it. It's a way to make ourselves feel better when we don't get something we want.