I don't know much about DirectX, so this is from an OpenGL specific standpoint. 3d graphics applications include shaders, which are programs that get compiled

I don't know much about DirectX, so this is from an OpenGL specific standpoint. 3d graphics applications include shaders, which are programs that get compiled by the graphics drivers and loaded directly into the graphics pipeline on the video card. The source code is standardized, but the binaries vary from card to card and driver to driver, so applications have to include the source and let the driver build it into working shaders. The text being processes is possibly shader source code.