There are three main types of lenses and zooms, there are fixed focal length lense, optical zoom lense and digital zoom lense.
With a fixed focal length lense the lense does not move at all (i.e no zooming), with these types of cameras the only way you can get close up picture is to move in closer, or if you are wanting to get a wide angle shot you will have to move back from the shot - but be careful to remember how the over all picture will look.
When a camera talks about its true zoom it is talking about its optical zoom lense, this is when the focal length actually extends and retracts. The image is magnified by the lense itself, using the optical zoom will always give the best picture over the digital zoom lense.
The third is digital zoom, this is when the camera does all the work instead of the lense. It enhances the central portion of the image in such a way that it actually degrades the over all picture. Unlike an optical zoom the actual length of the lens does not change at all.
This article does not cover dslr type lenses like wide angle lenses or telephoto lenses.
http://www.print-digital.info/articles/digital-camera-lenses.html
