What does Taoyuan Jieyi mean?

At the end of the Eastern Han Dynasty, North Korea's political corruption, coupled with years of famine, made people's lives very difficult. Liu Bei intends to save the people, and Zhang Fei and Guan Yu are also willing to do something with Liu Bei. The three of them hit it off and chose Zhangfeizhuang as the Peach Blossom Garden. At this time, the peach blossoms are in full bloom and the scenery is beautiful. Zhang Fei prepared a green cow and a white horse as sacrifices, burned incense and prayed, and took the oath. Three people recognized their brother by their age. Liu Bei became the eldest brother, Guan Yu the second and Zhang Fei the third. This is the famous "taoyuan sworn" in the romance of the three kingdoms.