The no parallax point–or nodal point–refers to the specific axis on a camera lens around which the camera rotates so as not to create a parallax error. By rotating around this point, the scenery will all move at exactly the same speed in the resulting pan shot.
When working with miniatures, this concept becomes essential when integrating models into the set. Unless there is no parallax in the pan, the model’s comparative size to the rest of the scene will be apparent.
Nodal tripods are designed specifically to rotate around the focal point of a camera’s lens. They are commonly used when shooting panoramic images consisting of multiple images stitched together, or for creating HDRI environment images for visual effects work.