The more the steering wheel is turned, the more friction the front tires create, which slows the car. Ideally the car is balanced, meaning that it has equal amounts of traction at the front and rear. Kenny Schrader flipped several times at 200-mph down Talladega's back stretch. It's bent, smashed, but didn't leak. Not just a fancy way to describe a gas tank, a fuel cell is a specially designed and manufactured device whose sole purpose is to increase safety.
Most racers consider the fuel cell one of the most important safety developments ever made.
The fuel cell is actually a bladder contained in a metal box. The bladder is designed so it can deform substantially without rupturing as a normal metal tank may do in a crash. In most cases a metal can contains the fuel cell bladder to maintain it's shape and volume. The metal also helps prevent sharp objects from puncturing the bladder. If the car rolls over, the balls fall onto seats that block the fuel from running out of the filler.