Does a race horse have rivals???

[IrishofNDMan]

While sitting in class today, I started to day dream and think about horse racing. I started to think about recent races that I watched, and just wondered to myself, "what drives these animals to want to run, and to want to run faster than the other?" What makes them want to win a race, are they truly competitors. Then I started to think, do some horses actually have rivals, and do they know when they are going up against them in a race? Might sound like a stupid question, but your thoughts please.