What's the practical difference between Virtual and Real?

I also wish to know much better in a comparison chart.
I'm a new user with no experience at all. But what I can understand is that vertex normals are handled differently. I'm not sure, but I was experimenting with real space and was preserving mu custom vertex normals (for hard surface industrial design modeling). Virtual space, I presume was making an average or I was having difficulties since my mesh does not come out from Blender Maya Max etc.
"RizomUV RS ((Real Spaces), is for CAD space RizomUV VS (Virtual Spaces) is our UV Mapping application for the CG industry".
What I was reading is that the precision is different.