A car stabilizer bar, also known as an anti-roll or anti-sway bar, is part of a car's suspension system. During sharp turns, a stabilizer bar keeps the body of the car from tumbling over.
During a sharp turn, the section of the car that is outside of the turn is forced downward, while the part of the car inside of the turn is forced upward. If the turn is fast enough, the wheels inside of the turn can potentially lift off of the road, which leads to the car flipping over. When the body of the car remains steady throughout a turn, all of the weight is evenly distributed throughout the tires.
The way that stabilizer bars work is that they shift the turning force from one side of the car's body to the other. Stabilizer bars are affixed to the car's frame in front of the front tires and are made so that the tires can rotate.
It's possible for a car to have too large of a stabilizer bar. When this happens, there's a decrease in independence between the suspension members on either side of the automobile. This leads to the stabilizer bar shifting force to the opposite side of the car whenever the wheel hits a bump. The best stabilizer bars are those that decrease body roll but still allow the tires to move freely.