An optical zoom is made to bring you closer to your subject, without you having to move. Zooms are constructed to allow a continuously variable focal length, without disturbing focus. To achieve this, the optical zoom uses a combination of lenses that magnify the image prior to being registered at high resolution by the sensor. While the digital zoom only changes the presentation of existing data, the optical zoom actually augments the data collected by the sensor. Optical zooms are superior to digital zooms.
A zoom allows objects at a distance to be magnified, or rather, zoomed. An optical zoom accomplishes this by changing the location of the lens, either manually or electronically.
Mechanical zoom, or the actual ability of a camera to bring distant pictures closer by moving the lens out of the camera.