The Raw GI Render Element stores how much indirect lighting (reflected diffuse light) is received by surfaces in the scene. This raw element is useful for fine-tuning indirect lighting in the compositing process.
The V-Ray Raw GI Render Element is untouched by the diffuse colors of the scene and represents the pure indirect lighting contribution. You can use this raw element to reconstitute the V-Ray GI by multiplying the V-Ray Raw GI with the V-Ray Diffuse.
This raw render element must be rendered along with the Global Illumination element ( V-Ray GI ) for proper results.