You can change a camera’s view by changing its Camera Properties, Film Back Properties, and Lens Properties. (See Camera Properties, Film Back Properties, and Lens Properties in Windows > Editors > Cameras.) You can also change a camera’s view using the camera tools (see the tools in the View palette).
Both zooming and dollying change the size of all objects in your scene as they appear in the camera’s window. Dollying, however, also changes the size of objects that are near the camera relative to objects that are far from the camera. Zooming maintains the relative size of objects in your scene. By dollying, you are moving the physical location of the camera; by zooming, you are changing the focal length of the camera’s lens.
Both tracking and changing the film back offset value change the position of all objects in your scene as they appear in the camera’s window. Tracking, however, also changes the position of objects that are near the camera relative to objects that are far from the camera. Changing the film back offset value maintains the relative position of objects in your scene.