How does it work?

The closest thing that I can think of to describe how sandpaper works is by comparing it to a saw. The sand particles on sandpaper have sharp edges that cut away at the surface just like a saw.

What is grit?

When we talk about sandpaper we reference it as XXX grit paper. This grit number refers to the number of abrasive particles per square inch on the paper. The lower the grit, the more particles per inch which makes it rougher. Higher grit paper has less particles making it smoother.