Spectrum of snoring and sleep apnoea

Snoring and sleep apnoea are related conditions: they are both caused by the upper airway becoming restricted.

Snoring is the result of partial restriction, while obstructive sleep apnoea is due to a complete collapse of the upper airway.

As the upper airway becomes restricted, the airflow through the restricted area flows faster and becomes more turbulent. This turbulent airflow causes the soft tissues in the airway to vibrate, which causes the audible noise of snoring.
More about snoring

If the airway becomes sufficiently restricted, it may actually collapse as a person is trying to take in a breath of air. Although the diaphragm is working hard to pull air into the lungs, the upper airway remains closed, preventing airflow into the lungs. This condition persists as long as the person remains in deep sleep. Eventually the remaining oxygen supply in the blood gets dangerously low, and a subconscious alarm bell rings to wake the person out of deep sleep. They may fully wake up, gasping for air, but more often they do not wake up into full consciousness before slipping back into deep sleep. The cycle of airway collapse, oxygen deprivation and arousal from sleep begins again... and again... and again.

After a night of being woken repeatedly, the person with sleep apnoea typically feels exhausted. Many sufferers report feeling as if they have not slept at all, because they did not get enough of the deep sleep we all need to feel refreshed.
More about sleep apnoea

A partially obstructed airway may cause an intermediate event called obstructive hypopnoea: this occurs when the airway is sufficiently restricted to cause shallow breathing, but not restricted enough to completely block the airflow.

Where are you on the spectrum of snoring and sleep apnoea?
A sleep study can help you find out.