If you look out into the distance, and move around, you’ll notice that objects closer to you move slower than objects further from you. This effect is called “Parallax”
Parallax is the observed displacement of an object caused by the change of the observer’s point of view. In astronomy, it is an irreplaceable tool for calculating distances of far away stars.
From “What Is Parallax?” on Space.com
In games, parallax is used to give the user a sense of depth. This repo will show you how to achieve that.
You can find the tutorial here.