What is the difference between falling asleep and passing out?

Sleeping is a state actively chosen by the manas; during sleep one is generally quite peaceful, able to rest at ease in the sleeping state. If the manas feels it has slept enough, or there is some matter to attend to, it will decide to wake up. Being knocked unconscious, however, is a passive and unwilling state. Because the body has been severely injured, the six sense objects cannot be normally transmitted to the supreme faculty (indriya), so the six consciousnesses cannot continue their activity, and the activity of the five aggregates has to cease. When the manas becomes aware of this condition of the five-aggregate body, it is extremely anxious and unwilling in its mind, and therefore it always seeks an opportunity to wake up. Once the body recovers a little, it will struggle to get up and move about; then, when the body truly cannot manage it, it falls unconscious again. Some people will even send their soul out of the body to inform their family and seek help from others. This shows that the manas is not willing to be knocked unconscious and be unable to use the five-aggregate body; it relies on the five-aggregate body to survive in worldly dharmas, and therefore it clings to the five aggregates and the six consciousnesses, unwilling to die and unwilling to remain unconscious.