Just the way sandpaper comes in various levels of abrasiveness and grits, the abrasives also have levels of grit up to 300 grit. The lower the level of grit, the coarser the tool will be. In the same way, if you want the concrete to have super glossy look, then finishing it with 3000 grit will give you the best results.
The First Grinding Process
When you remove a thick layer of the material to level it, the concrete itself becomes weak and this is where you need to add in a densifier that helps harden the concrete. This beneficial applicant helps to harden and solidify the concrete surface and gives you extra protection from staining and water penetration. The concrete needs to be hard otherwise it cannot get you the polish result that you are looking for. You may want to look up densifier as well if you want to learn more on the matter.