Trip difficulty levels: 

1 of 5: Easy
For all people in good health.  Those are trips with an elevation gain of 200-300 m and hiking distance up to 5 km and paths in good condition or easy terrain. 

2 of 5: Rather easy
For people who do some hiking and are used to the uneven terrain.  Those are trips with an elevation gain of 300-500m and hiking distance up to 10 km.  Here are some paths or a rather easy terrain. 

3 of 5: Moderate
For people who are physically fit and have some hiking or mountain hiking experience.  Those are trips with an elevation gain of 500-1.000m and hiking distance up to 15 km.  Rough paths or mountainous terrain. 

4 of 5:  Demanding
Only for people with mountain hiking experience.  Those are trips with an elevation gain of 1.000-1.400m and hiking distance up to 20 km.  Here we have a mountainous terrain with no paths. 

5 of 5: Strenuous
Only for people with a lot of experience in hiking/mountain hiking.  Participants must be physically and mentally fit for a long day(s) in the wilderness.  Those are trips with expedition level, elevation gain up to 2.000m and hiking distance around 20-25 km.  Rough mountainous terrain or glaciers.