Sway bars (also known as anti-sway bars, anti-roll bars or lower tie bars) affect the handling of the car on the lower end of the suspension. Sway bars tie the lower suspension components together across the front or back, and affect a car’s oversteer and understeer.
Sway bars will keep your car flat in turns instead of leaning over to one side. They distribute energy from the side of the car with all the force from the turn on it to the other side of the car, bringing the whole car down flat instead of leaning to one side. Of course the car will still lean some, but not as much.
Sway bars provide better cornering especially at high speeds and work very well in conjunction with strut tower bars. However, they can have an adverse affect in off-road situations by leaving one tire completely off the ground.