What is the difference between optical zoom and digital zoom when it comes to digital cameras?

I am looking to buy a digital camera and do not understand these options.

Optical zoom magnifies the image on the full area of the camera's imaging sensor, which means you get a photo will all the resolution the camera is set to deliver. Digital zoom uses a smaller part of the sensor to give the appearance of magnification. Photos taken with digital zoom will have lower resolution. In practical terms that means you will not be able to make as large a print with acceptable quality. For snapshot photography with the intent to make 4x6 prints and nothing larger, digital zoom is fine. Even inexpensive cameras in 2006 have enough resolution to stand a little digital zoom without hurting the quality of a 4x6. If you're a bit more into photos and like to make enlargements that look good, digital zoom will quickly become your least-favorite feature.

Optical zoom is the 'real' zoom and digital is just an illusion that is zoomed.

One should always lookout for optical zoom rather than digital zoom.

Optical zoom will give you a clean image that can be manipulated in a graphics program. Digital zoom is an interpolated image, similar to what you get from a scanner, and the image is not clean nor can it be as easily manipulated. I never let my camera go into the digital zoom mode.

Opitcal Zoom is the lens actually moving and making the image appear larger. Digital Zoom works by taking the image that is on the screen and simply magnifying it to make it seem closer, generally digital zoom isn't as good because it can make the end image appear grainy and pixelated. But the higher the optical and digital zoom the closer you can zoom in to take your picture.

Optical zoom is acheved through lens. This is best. The quality is the highest. Usually 2 to 4. I have seen as high as 12

Digital zoom is they take a small portion of the picture and enlarge it. This you could do it in the computer too. Digital zoom in digital camera doesnt make sense. They have it anyway.

Optical zoom:
A zoom lens is a mechanical assembly of lenses whose focal length can be changed, as opposed to a prime lens, which has a fixed focal length. They are commonly used with still and video cameras, some binoculars and telescopes, and other optical instruments.

Digital zoom:
Is a method of zooming on a digital camera either by increasing the size of the pixels in the image or by interpolating between them. The image doesn't physically get any closer and no extra information is collected, as the optics on the camera stay in place.