Horse Racing Forms give you information about the horses in race, including each horse's record and historical performance data.
The forms feature various numbers, letters, and symbols beside every horse’s name that offer this information.
First you'll find the race number and the horse’s starting position. You may also see the number of days since the horse last ran and the horse’s age.
Then, there's six numbers representing the horses’ most recent race results, listed in chronological order from left to right. If there's a letter or dash instead of a number, that usually indicates the horse did not finish the race. Different letters indicate the different reasons the horse did not finish the race.
You should also see contextual form data with letters that provide some information relevant to the race the horse is about to run. Things like a 'C' if the horse has won at this track previously.