Wikipedia
The most obvious difference between a Superkart and any other form of kart is that they have full aerodynamic bodykits and can race on car circuits over 1,500 metres in length. The power unit, most often, but not exclusively two stroke 250 cc engines, can be specially designed kart engines or production motorcycle engines with either five or six-speed sequential gearboxes. Owing to their high top speed and superb cornering ability, a Superkart's aerodynamic bodywork includes a front fairing, larger sidepods, and a rear wing. They use either tires and wheels and most often race on full size auto-racing circuits.
250 cc Superkarts often set faster lap times than much more expensive and technically advanced racing machines. Some British and Australian classes also include 125 cc gearbox karts.
Superkarts race on "long circuits" (e.g. Silverstone, Laguna Seca, Magny-Cours). In the UK they also race on "short circuits" (e.g. Kimbolton), "short circuits" are under 1,500 metres in length.
Superkarts are raced worldwide. There is a multi-event CIK-FIA European Superkart Championship (for 250 cc karts only), and there has in the past been a World Championship, which was last run in 1995.