We live on Earth. This is a place where a lot of energy is trapped in the atomic bonds to form a very dence form of Qi - the earthly matter. Life here is not so much dependent on our will. Rather, we have to obey a huge amount of laws that hold us within our physical limitations. In a way, Earth is similar to some far-away regions of Northern Siberia. It is cold here, and we have to fight all the time to survive.
However, being quite tangible and material, every creature on our planet is still suffused with all sorts of more subtle matter, given that the planets are still enveloped within the greater worlds formed from the subtle forms of Qi (see the pucture of the galaxy again).
This more subtle matter that we can only define as "energy" is a building material from which the subtle structures of our bodies are made. We cannot perceive these structures through our five earthly senses, because our five senses belong to the most gross "physical" realm, and their spectrum of perception is extremely limited. Click to learn how Chinese medicine treats Primary Infertility.
Furthermore, this "subtle matter" despite of constantly being produced and transformed by our bodies, does not accumulate in our system just by itself. The "subtle matter" however may be accumulated in the body counsciously and systematically, using certain practices and exercises, performed regularly.
Chinese Qigong is but one type of this exercise. Building up our Qi, just like we can build up our muscles, we are able to access subtle realms of the Universe and act from them, thus surpassing some of our physical limitations.