When you go to view/enter/pick winners 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 as much as you do, so they judge horses based on Fleet Figures and their overall grade. They also check the horse’s race history to see 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 predict whom the spectators will pick for the win. 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 trying to pick for yourself.