Lantingji xu is a piece of writing that was created a long, long time ago in China. It was written by a person named Wang Xizhi, who was really good at writing super pretty letters and words.
Imagine if you were practicing how to write your name with crayons or pencils. You would try really hard to make it look really neat and pretty, right? Well, Wang Xizhi was just like that, but a thousand times better! He was so good at writing, people would ask him to write important things like documents and letters.
One day, Wang Xizhi was asked to write something really fancy for a special party. So he wrote some special words about how important writing and reading are. He wrote those words on a big piece of paper with really beautiful characters and strokes. That piece of paper became known as Lantingji xu.
Today, lots of people still admire Lantingji xu and try to copy Wang Xizhi's beautiful writing style. Some people even think it is one of the most important pieces of writing in Chinese history!