What happens when a person chokes?

If food or liquid passes through trachea instead of passing through food tube or esophagus, choking occurs. Ask the person whether he chokes or not, if he answers that allow him to cough and get his wind pipe cleared. If he nods/gestures for your question, then you need to try Heimlich maneuver, a life saving technique otherwise the person will become unconscious and death may occur.