Back before the days of green screens and CGI people actually had to create real models of characters and settings to be used for movie effects. A matte painting is a painted representation of a landscape, set, or distant location that allows filmmakers to create the illusion of an environment that is nonexistent in real life or would otherwise be too expensive or impossible to build or visit. These paintings were created for use in "The Empire Strikes Back" and "Return of the Jedi" and show their creators in the process of painting them as well as the finished product.