The Bump to Glossiness texture node converts a normal or bump map into a glossiness map. This node allows a workflow to eliminate overly shiny or too glossy areas of an object. With a reflection glossiness texture generated from a bump/normal map, proper reflection glossiness is achieved at any distance, while detail is preserved.
The Bump to Glossiness node takes a bump/normal map and mixes it with a (separate) reflection glossiness map or value, and the resulting output is fed into the shader.
Note that the Bump to Glossiness node always outputs reflection glossiness.
Bump to Glossiness is not supported with V-Ray GPU, yet.