Qi is the continuum of matter and energy. It is both the grain of rice, and the steam which rises from the water as it boils.
Light sometimes behaves like particles (matter), and sometimes acts like waves (energy). This is Qi.
In Chinese Medicine, Qi is all of the body’s energies which create form, movement, function, and warmth.
The lungs breathe. The heart beats. The liver smooths circulation. The spleen digests food. The kidneys regulate Fire & Water. This is Qi.
Qi is the mother of blood. It is the refined essences produced by the organs to nourish and invigorate the body & mind.