The difficult art of predicting the winner of a horse race is called handicapping. The process of handicapping involves evaluating the demonstrated abilities of a horse in light of the conditions under which it will be racing on a given day. To gauge these abilities, handicappers use past performances, detailed published records of preceding races. These past performances indicate the horse's speed, its ability to win, and whether the performances tend to be getting better or worse. The conditions under which the horse will be racing include the quality of the competition in the race, the distance of the race, the type of racing surface (dirt or grass), and the current state of that surface (fast, sloppy, and so on). The term handicapping also has a related but somewhat different meaning: in some races, varying amounts of extra weight are assigned to horses based on age or ability in order to equalize the field.