Wikipedia
Bianwen is a technical term referring to a literary form that is believed to be some of the earliest examples of vernacular and prosimetric narratives in Chinese literature. These texts date back to the Tang Dynasty (618-907) and Five Dynasties (907-960) periods, and were first discovered among a cache of manuscripts at Dunhuang, Gansu Province, China in the early twentieth century.
The form originated in the popularization of Buddhist doctrine through storytelling and pictorial representation and was closely related to oral and visual performance. The stories were then preserved in written form, and the ways in which they were told influenced secular storytelling. Therefore, historical and contemporary stories were also found in the Dunhuang bianwen manuscripts. Popular stories include Mulian Rescues His Mother, which originated in India but was made into a Chinese legend by the bianwen adaptations. By the Song dynasty, however, the form had largely died out.
Their anonymous authors, although literate, were not educated members of the official class, and the tales were intended to be performed by people who could not read or write. Their language reflects the spoken language of the Tang period. The genres and themes of the tales were quite diverse and many of their forms and themes were significant in Chinese literary development.