Anyone who has sat through a fire safety course will be familiar with the diagram on the left. Even if you are not, the basic concept that all three elements from the sides of the triangle must be in place for a fire to burn is not hard to grasp. In Kung Fu we have a similiar triangle where all elements must interact to produce the goods. Above and beyond the mere kicks and punches, we must have good Chi or energy. We must have good Shen or mind and lastly good Jing which is hard to translate but roughly means structure or physical body.
Everybody pocesses each of these elements to some degree or other, some people may naturally excel in one particular area forming a kind of isosceles triangle. Kung Fu and Chi Kung training (really the same thing) will help you build your abilities in each element letting your own fire burn.