Life energy
Everything around us is energy, universal power, which moves the world. In different cultures this energy is called differently: in ancient Indien prana, in Japan ki and in China Qi (tschi).
According to chinese medicine Qi flows also in us. When the energy is in balance, Qi flows without disturbance, which maintains health.
If Qi flow for some reason will be disturbed, it causes energy stasis, or it decreases the energy. If the disturbance exists for a long time, it infuences the system stronger, which can cause more serious chronicle diseases.