These are endoscopic recordings of several individuals while they are breathing. Watching a person breathe can be a bit tedious, but it helps to orient the examiner to the motion of the vocal cords. Generally they open when you're breathing. They actually tend to partially close during breathing out (expiration) in order to keep the lungs inflated. It is very helpful to watch the motion of the vocal processes.
During sniffing, the vocal cord stretch and open wider. This is basically a reflex motion. In the last example, the video is taken after exercise and the opening is held even larger to move more air.
