Dollying is similar to zooming, in that the camera moves in toward (or away from) a subject. However, a dolly shot doesn't use the zoom control at all. In feature film shoots, a dolly is a platform that holds the camera and rides on rails similar to railroad tracks. When filming, one or more people (known as grips) push the dolly, resulting in a smooth shot.
When you zoom, the camcorder's lens is simulating the appearance of moving closer to your subject. When dollying, you're moving the camera physically closer. The difference is especially pronounced in the background (Figure 3.4).
Figure 3.4 These two shots are similarly framed, but look at the orange building in the background to see how the two approaches differ.