Megapixels in Digital Camera is a measurement of resolution of image. The image sensor record brightness levels on a per-pixel unit. A pixel is the homogeneously colored smallest unit of a digital image. 1 megapixel equals to 1 million pixels. Unlike other measures used in computing where the base is usually used for prefixes 1024 rather than 1000, in case of Megapixels it is 1000.
Understanding Megapixels
If you too much zoom a digital image in the screen of a computer, one can observe the pixels that make up the image. Images are formed as a series of pixels. Most of the devices used with a computer like a monitor, scanner etc. use the RGB model (Red Green Blue) or additive reflection model, except those that uses dyes, such as printers, which often use the CMYK model – Cyan Magenta Yellow Key (Key=Black) (model subtractive). The ‘sensors’ of our human eye has been classified using both RGB and CMYK model and others. Again, come back to pixels and megapixels, look at the header of this webpage – that logo. This page is being rendered by a 1200×800 pixels monitor in our case – that is equivalent to just over 1 megapixels. Now, if we take a screen shoot and zoom it :

We have zoomed only a part of that logo marked with a black rectangle and you can see the pixels as squares here that made the whole image of megapixels. The numbers are the hex values of the corresponding colors.
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Understanding?Megapixels in case of a Digital Camera
“Now ! Our this model got 12 Megapixels” – this typical marketing gimmick is used to trick the digital camera consumers, as most newbies has a belief that more Megapixels means more better camera. We have already said about this Megapixels related myth on our Digital Photography section. Megapixels can not really say about the quality of a digital camera but yes, this Megapixels actually says how bigger the photo can be printed out.
