Formula One, abbreviated to F1, is the highest class of open-wheeled auto racing defined by the Fédération Internationale de l'Automobile (FIA), motorsport's world governing body. The "formula" in the name refers to a set of rules to which all participants and vehicles must conform. The Formula One World Championship season consists of a series of races, known as Grands Prix, usually held on purpose-built circuits, and in a few cases on closed city streets.