The Journal ”CARBON” vol.6 5 ( 2 0 1 3 ) pages 1 – 6 propose a nomenclature for two-dimensional carbons materials

http://www.materialstoday.com/download/51110/

Hello Rachit, This is mostly a semantic difference. 

In principle as you know, graphene is referring to monolayers of graphite. So in principle Graphene nano-platelets should have a thickness distribution very sharp with mostly (in principle entirely composed of) dispersion of monolayers. On the contrary Graphite nanoplatelets may have a broader distribution of thicknesses, including thick (10 layers or more) platelets. Nevertheless, I would not be surprised that some people use the term graphene nano platelets to refers to thick (multilayered) graphite dispersions. What is mattering in-fine is the statistics of thicknesses that can be assessed by many technical means. 

thanks for your precious time and valuable answers...... it helped me a lot