Lens : the glass bit, over the hole in the iris (q.v.) which focuses the light entering the aperture. In a non-digital camera, it focuses the rays of light onto the film. The quality of the lens is very important.

Iris : the hole in the camera through which the light passes after being focused by the lens. Usually mechanically adjustable (think Stargate SG1....)

Shutter : device which when open allows light to pass through the lens and iris and when closed stops light from passing through; the faster the shutter opens and closes ("shutter speed") the less light passes through.

Good clear photographs need a combination of focus (determined by focal length of lens), aperture of iris and length of exposure (determined by shutter speed) all dependent on the subject and the conditions at the time.

Digital photography requires a digital camera from which images are saved on some form of computer recording device, e.g. floppy disk or image card. From there they are transferred to a computer for processing, printing etc. Digital photographs can be stored in digital form (e.g. on disk) or printed out as "hard copy" onto paper or card, either ordinary or special glossy card/paper.

Non-digital photography uses a camera which has light-sensitive film in it to record the images. This film then has to be developed into negatives - film images with the colours reversed- (usually professionally) and then printed onto special light-sensitive paper. Non-digital photographs have to be stored as negatives and photographs. Recent innovations include film processing outlets which will transfer the negatives onto digital format (CD).

My camera of choice is digital : on those rare occasions when I use non-digtals (such as those cheap disposables on holiday) I always end up having to scan the photos in anyway (I always forget to ask for a CD when I take the camera in for processing, and it's too late when I pick the prints up!)