A course is set up in a large parking lot defined by pylons. Each car takes turns negotiating the course while being timed. Speed is kept down to what one would experience on the street. Risk to the cars and drivers are very minimal. The majority of drivers compete in their regular street cars with little to no modifications.
People also race from open wheel cars to trucks.
Any car safe for use on the street is suitable for autocross. Car handling is more important than power. Skilled drivers in sedans often beat the novice in sports cars. Membership in the SCCA is not required to participate. A state driver's license is required.