Trekking generally means hiking in the high mountainous regions. But trekking in Nepal means much more..Trekking in Nepal means walking along the pristine forest of juniper and rhododendron through picturesque small mountain villages inhabited by diverse ethnic groups and meeting with the friendliest local people, traversing through isolated hamlets, following the scenic river banks, enchanting valleys, rocky gorges, terraced fields viewing mountain peaks, graceful waterfalls, watching variety of vegetations and wild animals, visiting monasteries and temples and breathtaking landscapes.
Trekking is possible any time of the year depending on where you are going. The popular seasons are spring and autumn. During winter, trekking is possible at lower altitudes. During the monsoon season, you can trek in the rain shadow areas north of the Himalaya like Mustang, Upper Manang and Dolpo. These places are out of reach of the rain clouds because of the high mountains and are unaffected by the monsoon. The best part about trekking in this season is that the routes are less crowded and if you happen to be a keen botanist, you will revel in lush vegetation as meadows blossom in full swing. To ensure quality service and safety, it is advisable to make the trekking programs through a government recognized trekking agency.
Everest Region
By name, you can guess it's the land of Mt. Everest (8850m), highest mountain in the world. This is one dreamed destination for adventerous lovers. Everest region was the main destination from early, even before Edmund Hilary and Tenzing Norgey Sherpa summit Everest. Everest Region is famous for Sherpas and Buddhist culture. Beside Mt. Everest , we can see the panoramic view of Lhotse , Nuptse, Ama Dablam, Pumori and Kwangde and other higher peaks. Also, Everest region is rich for ancient Buddhist monasteries.
Annapurana Region 
Annapurna Region is one of the most popular trekking destinations Nepal . This enormous forest of frozen Himalayan giants can be circumnavigated in a trek of 2 to three weeks, or it is possible to do shorter treks which bring you very close to the precipitous frozen slopes and glaciers. The Annapurna Sanctuary Pilgrimage trek takes you into the heart of a magnificent high valley surrounded by the Range. Each trekking is distinguished by a staff of well-known to local communities, experienced in trekking techniques and eager to make memorable trek, among the best one you have ever taken.
All Annapurna trekking start and end at Pokhara. It is possible to extend your trekking from Pokhara to Royal Chitwan National Park either by vehicle or River Raft for Elephant Safaris and game viewing or return to Kathmandu .
Langtang Region
Langtang-Helambu is in the north of Kathmandu . In this region Langtang, Helambu, Ganesh Himal will be covered. Gosaikunda ( Holly Lake ) and panoramic view of surrounding mountains are major attraction of this region. Langtang was declared National Park in 1976 and is a natural habitat of more than 1000 plants, 150 birds' species and numerous other mammals. Trekking will be started from Dhunche or Shyabru Bensi.
Dhaulagiri Region
Dhaulagiri (White Mountain), separated from the Annapurna region by Kali Gandaki Gorge (deepest in the world) includes some fifteen peaks above 7000mt. The trekking in this area is relatively strenuous and needs some mountaineering knowledge. Magdi Glacier, Dhaulagiri Base camp (4750m), French Pass (5360m) (highest point of the trek) including the several peaks such as Putali Himal and Tukuche Peak gives you an excellent view of Dhaulagiri range. A hidden snow valley (after crossing French pass) gives you a heavenly test of white world. The Dhampus Pass between Tukuche peak and Thapa peak is another haven in the trip.