What's the difference between pipa and Ruan?

Qin Liu is a pipa plucked instrument. Because it is made of willow, its shape is similar to that of willow, so it is called Qin Liu, or "Qin Liu". Qin Liu is very similar to pipa in appearance and structure. The earliest Qin Liu had a very simple structure. Because of its rural and folk appearance, Qin Liu is affectionately called "Tupipa" by China people. "Pipa" has been popular among the people in Shandong, Anhui and Jiangsu provinces of China for a long time, and has been used to accompany local operas.

Qin Liu is not only the same as the pipa in appearance and structure, but also plays the pipa in the same way, only playing plucked balls. When playing Qin Liu, the player should sit up straight, put Qin Liu on his chest, hold the piano in his left hand, press the strings with his fingers, and pluck the strings with his right hand between his thumb and forefinger, which is very elegant.

As for Ruan, I don't know yet.