The program uses real star data to to show you what you'd see if you wandered into proximity with a black hole -- like how the extreme gravity would appear to "shred" background constellations of stars, "spinning them around as though in a giant black washing machine." More details from NewScientist:
The program's creators say it could be an excellent tool to familiarise people with the weird ways that black holes warp light. "It's useful for people to play around with the parameters to study how, for instance, a black hole would distort the constellation Orion," says Thomas Müller of the University of Stuttgart in Germany.
A black hole forms when a massive star explodes at the end of its life, the core collapsing to a point with huge density and an enormous gravitational pull. Even at a safe distance from the black hole, its gravity can distort the apparent positions of background stars, an effect called gravitational lensing.