Grinding a surface will smooth out imperfections and open a new layer of your stone upon which it is possible to build a high quality honed or polished finish.
Grinding will remove deep scratches, stains and other contaminations from your stone, resulting in a very smooth and even surface, able to reflect light more consistently. Grinding will also remove any lippage, the term used for uneven tiles which can occur after a typical installation.
Resurfacing is an extremely skilled task that requires patience and experience. If not done properly and to the right depth it may only enhance the scratches and impurities.