One of the reasons horse betting is exciting is that the odds fluctuate every time someone places a bet. This fluctuation is referred to pari-mutuel wagering, or sometimes pool betting. In standard betting games, you are usually betting against the house. When it comes to horse racing, you're betting against other betters. Once the winning horse crosses the finish line, the house deducts its take, and what remains is divided among those who bet on the winning horse.