For 1990-2009 cars

Toe is a measurement of how much the front and or rear wheels are turned in or out from a straight ahead position. When the wheels are turned in, toe is positive (+). When the wheels are turned out, toe is negative (-). The actual amount of toe is normally only a fraction of a degree. Toe offsets the small deflections of the wheel support system that occur when the vehicle is rolling forward. In other words, with the vehicle standing still and the wheels set with toe-in, the wheels tend to roll parallel on the road when the vehicle is moving.

Incorrect toe adjustment will cause premature tyre wear and cause steering instability.