There are many different reasons why someone could be snoring.
Here are some examples for you:
Sometimes people can start to snore when they gain more weight (become fat). The reason this happens is because the accumulation of fat reduces the size of the passage through which the air passes when the person breathes. “Pushing” air through a smaller passage creates sounds. This is also why one of the first things the doctor will tell the person is to lose weight.
In other cases, certain parts of the mouth (uvula – see the picture here) again obstructs the passage while the person is breathing and its vibration causes snoring. There are treatments like tonsillectomy which remove some or all of the parts which are blocking the breathing channels.
Nasal strips For Snoring
The above 2 examples occur with mouth/throat blockage. But there can also be a nasal congestion. Basically the same logic, the air path is reduced causing snoring. Nasal strips work really good for people who have this scenario.