If you like to know more details, there is a book name searching for
The Ancient Tea Horse Road.

http://www.tearoma.us/product/search...tea-horse-road

The Tea Horse Road wound its way through Yunnan, traveling thousands
of kilometers down paths, round trails and over bridges, spread out
like a web with strands reaching as far as Tibet, Burma, India and
Nepal. The brave men who carried tea along this road faced arduous
cliffs and bridges, harrowing cable-crossings, bandits and thieves and
the loneliness of the mountain nights. Even the tea itself seemed to
grow wiser for having made the journey, though this great road carried
much more than tea; it was as much a cultural thoroughfare, blending
ethnic groups, art, music, religion and folklore. And though the old
trails are paved over, and it is now trucks rather than horses that
carry most goods, the heroic men who blazed these trails can still be
heard in the distance”€laughing and singing to the beat of the jangling
bells and clopping hooves.