What are Snoring and Sleep Apnea?
Noisy snoring is usually caused by a restricted airflow at the back of the throat. This happens when the soft tissues there close up, so air has to be forced past them. This causes the soft tissues to vibrate loudly - causing snoring.
Obstructive Sleep Apnea (sleep apnoea) is when the airflow is so restricted the throat completely closes, stopping breathing. This triggers a choke reflex to clear the airway, disrupting sleep. More on sleep apnea...
Snoring and sleep apnea happen when asleep because the jaw muscles go slack, so the lower jaw and tongue fall back, narrowing the airway.
This effect is made worse by laying on your back, causing the lower jaw to fall back more. Snoring is also worse when overweight, or relaxed after a drink or two.