As the name makes clear, tea and horses were the major commodities traded along this route from the Tang to the late Qing Dynasties, from around 600 AD to the 20th century. Trade and travel definitely took place along this route for several thousands of years before the Tang, as archaeological sites in Tibet and in the city of Chengdu demonstrate, but for us, this period is the most significant.
Yellow tea might be a good tea for Westerners, because some do not like the grassy flavor of green teas, but they want the same health benefits that green tea provides. Yellows might just be the “in-between tea” that people here in the US could enjoy for both taste and health benefits.
There’s a lot of web-literature about tea out there, and the drink is now becoming popular, but actual knowledge and experience drinking tea is still somewhat lacking. This is a good thing, because it allows tea merchants to organize tastings for “tea newbies” and observe and enjoy everybody’s reactions as they drink their first good green tea, their first Da Hong Pao, their first aged oolong.