When talking about cars and tires, camber refers to the
angle between the
tire and the ground. Zero degrees of camber means that the tire is perpendicular to the ground. Positive camber means that the top of the tire sticks out, while the bottom is tucked underneath. Negative camber, which is much more common in
racing applications and even on
street vehicles, means that the tire is tilted inwards at the top and outwards at the bottom.
This helps to offset body roll during turns; as the car's inertia causes the inside of the tire to lift and the outside to be pressed down harder, having negative camber means that the contact patch is actually square, and each bit of rubber is subject to the same amount of weight, and is therefore putting forth the same amount of force to make the car turn.