Simplify the following text for a Grade 8 native English-speaking person.
Original: Kart racing or karting is a variant of open-wheel motor sport with small , open , four-wheeled vehicles called karts , go-karts , or gearbox\/shifter karts depending on the design .
Simplified: Kart racing or karting is a type of open-wheel motor sport . It uses small , open , four-wheeled vehicles called karts , go-karts , or gearbox\/shifter karts depending on the design .