What is meant by parallax of a point on a photograph?

Simple parallax is the angle produced by the difference between the axis of a viewing optic versus the axis of the image forming lens. In non slr cameras (range finders) this is an issue below a certain distance and causes a different image to be captured than what is viewed.

The "no parallax point" is the point around which a camera would have to be rotated when constructing panoramic photos using a series of images, so that when the images are stitched together, there is perfect alignment. Where this point is exactly was a subject of debate. Search "no parallax point" to learn more and decide how to find this point in your lens(es).