The amount of detail that the camera can capture is called the resolution, and is measured in mega pixels (MP). The more mega pixels a camera has, the more details it can capture and the larger pictures can be without becoming blurry.
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The number of times the image can be enlarged with the optics of the camera. The optical zoom 'moves' you closer to the subject without sacrificing quality. The higher the optical zoom, the farther away you can be to take a photo and still get a clear, close-up image.