When you go to view / enter / wager on a race, you're not the only person at the track. In addition to players, the track has an Odds Maker who attempts to  put odds on each horse entering the contest.

The Odds Maker is pretty smart, but they aren't perfect. They can only see what you do, so they judge horses based on the grade, attributes, and preferences listed. They also check the horse's race history to get a sense of how well they've run before. The more races a horse has run, the more accurate their odds are.

However, the Odds Makers isn't exactly trying to predict the winner of the race. Morning Line Odds are a prediction of how the Odds Maker expects people to bet. If a horse has won recently, won at this distance, or is a fan favorite, the Odds Maker might favor it. Keep that in mind if you're eyeing the odds for your own bet.

Reading odds is pretty simple. Every horse has a value with a number on the left and a separate number on the right "6/1." The number on the left is the how much you could win; the number on the right is how much you bet.  For the 6/1 each Derby you bet would win 6 Derby if that horse won the race.