Polished concrete is becoming more and more popular in the commercial and retail settings due to its attractiveness, longevity and easy maintenance. Polished concrete is achieved through a process of progressively using finer and finer grits of Diamonds to create a high-gloss shine.
A good analogy is sanding wood. Staring with more aggressive grit to remove any imperfections in the surface and then moving to a finer and finer grit until you achieve the finish you are wanting