Generally, in my understanding, they remove the burr and/or refine the finished edge and make it smoother. It will polish the edge somewhat, but will not make it a mirror finish. If used with a compound containing some kind of abrasive, it will also tend to grind the apex somewhat. More knowledgeable people than me may give a much better explanation, or refute what I think. I am a nooobie at this and am only guessing based on some observations from my use of strops.