'Toe' is the term given to the left-right alignment of the front wheels relative to each other. Toe-in is where the front edges of the wheels are closer together than the rear, and toe-out is the opposite. Toe-in counteracts the tendency for the wheels to toe-out under power, like hard acceleration or at motorway speeds (where toe-in disappears). Toe-out counteracts the tendency for the front wheels to toe-in when turning at motorway speeds. A typical symptom of too much toe-in will be excessive wear and feathering on the outer edges of the tire tread section. Similarly, too much toe-out will cause the same feathering wear patterns on the inner edges of the tread pattern.
Camber is the tilt of the top of a wheel inwards or outwards (negative or positive). Proper camber (along with toe and caster) make sure that the tire tread surface is as flat as possible on the road surface. If your camber is out, you'll get tire wear. Too much negative camber (wheels tilt inwards) causes tread and tire wear on the inside edge of the tire. Consequently, too much positive camber causes wear on the outside edge.
Negative camber is what counteracts the tendency of the inside wheel during a turn to lean out from the center of the vehicle. 0 or Negative camber is almost always desired. Positive camber would create handling problems.The technical reason for this is because when the tires on the inside of the turn have negative camber, they will tend to go toward 0 camber, using the contact patch more efficiently during the turn. If the tires had positive camber, during a turn, the inside wheels would tend to even more positive camber, compromising the efficiency of the contact patch because the tire would effectively only be riding on its outer edge.
Another possible reason for abnormal tread wear is incorrect inflation. Tires should be inflated as per the car manufacturers instructions. If the tire is under-inflated the outer sides of the tread wear off faster. Also when the tire is under-inflated it generates excess of heat and may explode at high speeds. Similarly, if the tire is over-inflated, the center part of the tread wears off faster. In this case the contact patch of tire with the surface of the road is not sufficient and the stability of the car is decreased.