Exposure is the result of the amount of light that reaches the camcorder sensors (CCDs.) The amount of light is controlled by opening and closing the iris which acts like the pupil of the eye for the camcorder and the shutter speed. Exposure can be adjusted automatically or manually on the camcorder.
Focus is the sharpness of the video image. Focusing can be done either manually or automatically. These days, most of the camcorders have great automatic focus. This should be enough for most cases but sometimes you need to set the focus manually (e.g. having two objects in the frame one very close and another one far from the camcorder). Setting focus manually is different from camcorder to camcorder, but most of the time, camcorders have a ring around the lens called focus ring, for this purpose.
This involves adjusting the camcorder in different lighting conditions (e.g. indoor, outdoor) to record the white color, white. If the camcorder is not adjusted for the correct light condition, colors will not be recorded correctly. So, white color will not look white in the recorded video. All the camcorders have automatic white balance that adjusts the camcorder with varying lighting condition. White balance may also be set manually (look for manual white balance in your camcorder settings.)
Zoom is used to make the object appear closer or further away without changing the camcorder position. This is done by using a set of lenses on the camcorder called zoom lens, or by digitally processing the video image. The first is called optical zoom and the latter is digital zoom. Digital zoom reduces the quality of the video drastically and it is not recommended to use it. The zoom power is measured by ‘X’ in camcorders. For example, 18 X optical zoom means that camcorder can magnifies the object 18 times