@Danique "Knocking out" or "Getting knocked out" is just a simple way of saying loss of consciousness. A blow to the head can cause someone to lose conciousness, but it risks physical trauma and a concussion. By choking someone, you restrict air supply to the brain forcing unconsciousness. If done properly, it is less risky as there is no physical trauma. In both cases the person is unconscious.
@Frank Horrigan I didn't mean to the head as the other person said I watch too many movies, but in those movies. You can hit the person on the back of the neck and they'd loose consciousness