Round file/rods

What is "file" in Round file?

The rods here are of any kind? or just generally speaking? they don't mention anything more about these rods.

A lot of people need to sharpen serrated edges, and we can do that on this. Most of time the backside of a serrated edge is flat, so what we do, is come up the backside with the honing belt to flatten the back of the serrated edge, to match up with the manufactures grind that's put on the front. So that saves time for the user instead of having to use a round file or one of those rods.