Nasal pillow is stuffed inside the nostrils, for the ventilator treatment pressure is not high for the user can choose this, because in the face of a smaller area, you can wear glasses, watch TV and so on.
Nasal mask also has a variety of more comfortable dynamic or gel mask. Economical ones have boutique nasal masks and other, slightly less expensive options.
Oral-nasal mask as the name suggests is a mask that completely covers the mouth and nose, in the face of the largest area of coverage, generally used in the lung function is not good for the user. The silicone is relatively thin, and care should be taken when using it.
The masks introduced above are ResMed's masks. The patent is the largest, and the choice of people is wider, just for reference.