This instrument employees a specific type of sound generating mechanism derived from musical instruments made and used by pre historic Native Americans. The Native American flute can also be designated as a two chambered duct flute. The two chambers are the Slow Air Chamber at the head or mouth end of the flute and the Sound Chamber or barrel of the flute. The Sound Chamber is where the finger holes are. Separating the two chambers inside the flute is a solid area of wood called the plug. Connecting these two chambers is a duct or channel. This channel directs the air from the slow air chamber against the splitting edge of the sound chamber and starts a sound vibration.
The Native American  flute is a type of whistle flute. Like the Irish penny whistle or the recorder you do not have to develope the musculature around the mouth (called embouchure) to make a sound. All you have to do with the Native American flute is put your mouth to the end of the flute and blow into the hole.
The other types of flutes - side blown flutes like the silver concert flute, bamboo bonsurai or end blown flutes like the Anasazi flute or Japanese meditation flute require the player to hold the mouth muscles and lips in very specific ways to make a sound.