Snoring is caused by a partial obstruction of your breathing while you sleep.
When you sleep, the muscles in your tongue, throat, and soft palate (a.k.a. the roof of your mouth) relax.
If these muscles relax too much, they’ll block your airway. That will cause the muscles to vibrate as your breathe, and that’s what causes the buzzing sound associated with snoring.
The more narrow your airway is, the more the muscles will vibrate, and the louder your snoring will be.