This app allows you to edit little programs called Shaders, in the GLSL language.
These programs are graphic programs that run on the GPU and run very fast. You can make 2D shaders or 3D shaders with distance fields.
If you decide to make a 3D shader you can view them in Virtual Reality with Google Cardboard.
If you want to see example of shaders you can check http://glslsandbox.com or http://shadertoy.com.