Knowledge of Ki-energy is extremely beneficial prior to beginning the Dahn-Jon Breathing exercises. Ki-energy flows through the human body in three different ways:

Won-Ki, Jong-Ki and Jin-Ki. “Won” means “innate,” “Jong” means “stamina or strength,” and “Jin” means “true or genuine.”

1) Won-Ki : The first type of Ki-energy is inherited energy Human beings receive this energy at birth from their parents.
2) Jong-Ki : The second type of Ki-energy is acquired energy from nourishment. This energy source is replenished through diet and respiration.
3) Jin-Ki : The third type of Ki-energy is received through relaxed concentration.

From Dahnhak book by Ilchi Lee