What's the difference between the posterior nasal sound and the anterior nasal sound?

The front nasal sound ends in n and the back nasal sound ends in ng. When making nasal sounds, press the root of the tongue against the upper jaw to let air flow out of the nasal cavity and make nasal sounds. N is suitable for flat head.

Posterior nasal sound, when pronounced, the tip of the tongue is pressed against the upper gum; Ng is the nasal sound at the root of the tongue. When you pronounce this sound, you should rest the base of your tongue on the soft palate.