Beginning

The four elements are Air, Water, Earth, Fire and in that specific order. The physical elements, like actual water, are only symbols and examples of what they represent. The arrangement of the elements are within a circle and are set to the way each element relates to the other. For instants, Water is diagonal to Fire because they conflict with each other, an opposite if you will,  and are next to elements that relate to each other progressively, example: Earth is next to Water because Water is within Earth and Fire is next to Earth because Earth fuels Fire. Therefore the organization of the elements looks roughly like the graph made by the philosopher Empedocles. The Elements represent the sub elements; Water has > Ice, Foam, and Mist, to name a few, which are more specific and are actual connections to the physical aspects of nature. 
The Four main elements are under the two principle elements. These elements are more arcane, but are more widely known, both metaphorically and literally.  They are Light and Dark.