SLR - (Single Lens Reflex) - The same camera lens is used for viewing as for shooting. An advantage of this mechanism is that the photographer sees exactly what the camera lens will place in the photograph; a disadvantage is a more substantial camera body.
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.