What do you mean, spring and autumn are divided into five, and poetry into four?

During the Spring and Autumn Period, the world was divided into five vassal states. Spring and autumn are divided into five, and poetry is divided into four. This sentence comes from an article in Zhuangzi to the effect that during the Spring and Autumn Period, the world was divided into five vassal states, and there were four different poetic styles and schools at that time. This metaphor satirizes the political and literary environment at that time, and expresses Zhuangzi's dissatisfaction with the times and his call for people to pursue truth.