Megapixel - (One Million Pixels) - Refers to the resolution of a digital camera's image. A 1-megapixel camera will produce a digital image using one million individual information points, approximately 1200 pixels wide by 900 pixels high.
Optical Zoom - Physically changes the focal length of the digital or analogue camera using the lens (optics).
Digital Zoom - The camera uses digital wizadry to manipulate the camera's digital image to simulate an optical zoom. This will result in some degradation of the digital image's quality.