Members of each category have common attributes and obey the same laws. Members of different categories also interact between themselves according to some consistent laws. The attributes of the categories and their laws of interactions are similar to the attributes of natural elements and their laws of interactions. Therefore, each category is given the name of a natural element which best represents its attributes and laws of interactions. The name of the five categories are Metal , Wood , Water , Fire and Earth .
Fire produces residue which settles down to form Earth.
Earth is the source of Metal. Metal melts and become like Water. Water in turn helps Wood to grow. Each element in this cycle produces the succeeding element. The destructive cycle - Wood destroys Earth by getting nutrients from it.