Original: Sidecar-cross racing, also known as sidecar motocross, is very similar to regular, "solo" motocross but with a different type of motorcycle chassis, and with a team of two people riding together instead of one, a "driver" and a "passenger".
Simplified: Sidecar-Cross racing, also known as Sidecar Motocross, is a race that uses a different motorcycle chassis than regular motocross. It also uses a team of two people riding together, a "driver" and a "passenger".