Yeah there are two(or 3) things, and neither has exact name so every renderer has named it differently, or didn't give it name at all :- ).
Here is brief summary (sorry for off-topic to anyone):
- Glossiness or Roughness range : This described how rough a material can get. Previously Corona with Glossiness 0 was something equivalent to 0.4 in fact, it was still very glossy, definitely not fit for paper/sand/etc.. SOLVED in both Corona and Vray.
- Specularity intensity based on Fresnel: Both Vray and Corona had BRDF which didn't properly dim the specular intensity when glossiness was getting lower. So 0 glossiness was literally shining (the haze), when it was supposed to be almost fully flat. SOLVED in both Corona and Vray
- Glossiness value changing based on fresnel term. This is effect that makes materials more glossy (mirrory) towards the grazing angle even if they are rather dull otherwise. Disney calls it "retro-reflection" in short, and it can actually work both ways, making dull/rough materials more shiny at grazing angle, and opposite, shiny materials getting little bit more dim at grazing angle.
Neither Vray or Corona supports the last feature through some exposed parameter. F-Storm currently does support it, although I don't think it's part of BRDF, so you can simulate the same effect yourself manually by placing your glossy node network (or simple texture/value) into fresnel node.