In Chinese philosophy, things in nature can be classified in 5 types: wood, fire, earth, metal, water. Most Westerners fail to understand the concept because they tend to take these names literally. These five elements are not just the matters that the names refer to, but rather metaphors for describing how things interact and relate to each others.
It is believed that wood produces fire; fire produces earth; earth produces metal; metal produces water; water produces wood. On the other hand, wood controls earth; earth controls water; water controls fire; fire controls metal; metal controls wood. These interactions and relationships forms a framework for different schools of philosophy, belief and discipline. The interaction of five elements becomes a tool that helps scholars sort out observations and empirical data. Based on observations of how things interact, things are classified into one of the five elements so that they fit into the observed pattern. Then one can draw high level conclusions or predictions based on the types.
Also The Chinese believe there are five seasons - Autumn, Winter, Spring, Summer and Late Summer. Behind each of the seasons there is an elemental energy; the Five Elements - Fire, Earth, Metal, Water and Wood actually creating each of them. By observing nature we can see these five energies in the world around us and also see how these same energies are reflected within our own bodies and personalities.
For example Spring is the beginning of the season cycle, a time of birth and new beginnings. It is also the energy of the element Wood. This is the energy that brings forth new growth. It is the energy that pushes the new grass through the snow and produces new leaves. It does this so nature can take in nourishment.
Spring is also the time of hope; it bursts forward with optimism, offering change after the quiet, still time of Winter. It brings to life the potential inherent in the each dormant seed, awakening, growing. Think of the wood of a tree, it gives nature structure and shape but does not let anything hold it back as it grows. Without change all things would wither and die.
The principle of the five elements have a deep root in the Chinese culture.

source: http://nostalgia.wikipedia.org/wiki/Chinese_element