As already mentioned, it's for honing. The difference is that sharpening involves removing metal to create a new edge, while honing simply bends the edge back to being straight. Although we think of steel as being a hard material, the edge of a knife is thin enough that it gets bent to one side or the other just through normal use. Using a honing rod to push the steel back to where it belongs means the knife feels sharper because you're now cutting with the actual edge.

What I found interesting when learning more about sharpening is that you’re actually looking for the edge of the blade to bend. That bend creates the “burr” and you can feel it by running your finger along the flat of the blade towards the edge. A consistent burr across the blade is one way to know it’s sharpened enough. Then you hone that burr until it is straight.

When you no longer have a burr which can be honed, it’s time to sharpen again.

It's not, it's for honing

and til the difference between (and that there was a difference between) honing and sharpening.

It's a honing rod or honing steel. Honing isn't exactly the same thing as sharpening, but yes it will help the knife cut better.

I've heard it explained that honing is for improving the cutting edge you have, and sharpening is cutting a new edge.