Definitions for "Megapixels"
Maximum real megapixels - millions of pixels.
Referring to millions of pixels or dots in a digital photo's resolution. A digital camera can have a CCD that's rated 4.2 megapixels but delivers an effective resolution of 4.0 megapixels. The higher the effective resolution, the higher the quality of the picture that can be recorded.
An indication of the amount of image information that can be captured by a digital camera. To oversimplify, the higher the megapixel rating the higher the overall image quality. There are many other factors that affect image quality, with lens quality near the top.