All over the world, ski resorts divide trails into four categories depending on the steepness and the degree of difficulty of the trails. The trails are marked by signs placed in the beginning and in several places along the trail. There are two systems of categorizing ski trails - the European and the American system.

In Europe green and blue markings indicate easy beginner trails. Red indicates a trail of medium difficulty and black indicates a trail reserved for absolute experts.

In North America as well as in New Zealand and Australia the American system is used to mark ski trails and to indicate different categories of difficulty. This system has four categories. Green indicates a beginner trail. Blue is used to mark an intermediate trail. Black indicates a ski trail designed for experienced and expert skiers and "double black" markings indicate an extremely difficult trail, often with moguls on it.