What is parallax mapping?
Check the long description.
Stellar parallax is parallax on an interstellar scale: the apparent shift of position of any nearby star (or other object) against the background of distant objects. Created by the different orbital positions of Earth, the extremely small observed shift is largest at time intervals of about six months, when Earth arrives at exactly opposite sides of the Sun in its orbit, giving a baseline distance of about two astronomical units between observations. Astronomers use Stellar Parallax for mapping nearby stars and mapping our observable universe.
Parallax mapping is an enhancement technique applied to 3D textures in game design. It creates levels of textures and a mixture of bump mapping/normal mapping to create a more realistic outcome and more depth.
So knowing what stellar parallax is you can see how this applies to it, and how it would be used for creating 3D models of our universe.