Snoring and Sleep Apnoea
Snoring is simply the noise made when the soft tissues in the airway vibrate as air passes.
The narrower the airway the faster the air must travel, and if the soft tissues are relaxed and flabby (when asleep) the more they vibrate and the louder the noise.
You can snore and not have Sleep Apnoea, and you can have Sleep Apnoea without snoring, but they usually go together
Apnoea (or Apnea if you are American) literally means "without air", so breathing Stops.
Narrowing or total closure of the airway during sleep can cause Obstructive Sleep Apnoea and snoring. A less common form is Central Sleep Apnoea when the body decides not to breathe, such as at high altitude.