What is the purpose of the ring in the middle of the Nikkor 18mm - 200mm lens?

The ring goes from infinity to 3 ft. I misplaced the manual but I believe it was for macro photos which I don't do. Also does it have a name? It moves automatically depending on shutter and aperture.

No, it moves automatically as the camera focuses - it's the manual-focus ring.

It's unusual for a budget-priced lens to have a distance scale on it (third parties often include one, but not manufacturers), but not unknown.

The scale is the focal distance to the subject. 3 feet is the closest it will focus, and infinity is the furthest. Nothing to do with macro, although your camera may have a closeup mode that comes close to macro.

If you have it in AF, it moves on its own. If you put it in MF, you get to do the focusing. Of all the crazy names, it is called a "focusing ring".