Like most consumer-grade variable aperture zoom lenses, this lens is a series of compromises carefully designed to do many jobs reasonably well. While, for example, it will take a very good photograph at 100mm, it will not have the same image quality from the center all the way to the corners as, say, a Zeiss Makro-Planar 100mm lens. However, it also doesn't cost US$1800 for a single focal length!
Likewise, this lens has a reasonable macro capability, meaning that it can make macro photographs at a reproduction ratio of 1:2, meaning that objects will be reproduced at 1/2 life size on a 35mm sensor or film. In comparison, most purpose-built Micro-Nikkor lenses can make photographs at a reproduction ratio of 1:1 or life-sized. For example: http://www.nikonusa.com/en/Nikon-Products/Product/Camera-Lenses/AF-S-VR-Micro-Nikkor-105mm-f%252F2.8G-IF-ED.html
As in all things in life, compromises are made as to cost, quality, weight, complexity, et al.