Directional tyres are marked on the side, i.e. on the tyre's sidewall. You will see the word "Rotation" or "Direction" written here. Next to it, there is a small arrow which indicates the tyre's forward direction (rolling direction).
Directional car tyres: What is special about them?
You might have noticed it before: Directional tyres have a "V" shaped profile as opposed to a "U" profile. This not only looks sporty, but also fulfils a special function: The arrangement and the inclined shape of the tread grooves ensure that any water is channelled very quickly onto the road and discharged immediately to the outside.
This feature gives you special protection against aquaplaning. But not only that: the special profile shape also ensures stability at high speeds as well as on snow-covered ground. This is why winter tyres are often directional.