Easy Trekking: It entails an easy walking terrain with minimum ascents. Easy treks can be done in 1-3 days depending on the distance.
Moderate Trekking: It entails a slightly difficult terrain which means you are required to walk on some challenging stretches with ascents. Most of the moderate treks are at or above the height of 3000 m.
Difficult Trekking: It entails long and difficult terrain that requires a lot of physical fitness. There are steep ascents and descents, crossing over boulders and even wading through water is required at times.
Alpine Trekking: It entails trekking in a high altitude region i.e 4000 m onwards. This kind of trekking sometimes is quite challenging and requires proper acclimatization and expertise.