Focus curiosity about the Nikon D7000?

I had a Nikon D5100. And I chose to upgrade a new camera so I just recently bought the Nikon D7000 with the 18-105 lens. And as I tried on the lens, and had the auto focus on, I can still do manal focus. Why is that?

The lens probably has a switch that says AF-M or M. The AF-M is the auto-focus position, but it allows manual over-ride with no further settings.

. Because that is how it has been designed. No problem with the lens. Even with AF on you can still move the ring and do the manual focus. Ease of use!

It is called "full time manual focus". If the autofocus isn't quite where you want it you continue to hold the shutter half pressed and tweak the manual focus before you press the shutter.