Tires generally fall into one of the following categories:
Directional tread patterns are designed to provide a range of attributes during particular driving conditions.
The tire can only be mounted to the wheel so that it revolves in a particular direction to correspond with the tread pattern.
An arrow on the tire sidewall indicates the designed direction of forward travel.
Non-directional tread patterns are designed in such a way that the tire can be mounted on the road wheel for any direction of rotation.
Symmetric tread patterns have the same tread pattern on both sides of the tire and can generally be classified as Non-directional tires.
Asymmetric tread patterns have a tread pattern that is different from one side of the tire to the other.
They are designed to provide good grip when traveling straight and in turns. They are generally directional tires and must be fitted to the road wheel in accordance with the fitting instructions to ensure that they perform as designed under operating conditions.
Summary
Tire treads can be directional, non-directional, symmetric and asymmetric.
Source: CDX Global & Wikipedia - en.wikipedia.org
