"The digital sensor in the majority of digital cameras is what is known as a BAYER PATTERN sensor. This relates to the arrangement of red, green and blue sensitive areas ... Each pixel in the sensor responds to either red, green or blue light and there are 2 green sensitive pixels for each red and blue pixel. There are more green pixels because the eye is more sensitive to green, so the green channel is the most important. The sensor measures the intensity of light falling on it ... A conventional digital image has pixels which can be red, green, blue of any one of millions of other colors, so to generate such an image from the data output by the sensor, a significant amount of signal processing is required. This processing is called Bayer interpolation because it must interpolate (i.e. calculate) what the color of each pixel should be. The color and intensity of each pixel is calculated based on the relative strengths of the red, green and blue channel data from all the neighboring pixels."If you have been confused about how images really work, i.e. what are pixels and how is the color stored in each pixel of the image, this article does a good job of giving all the basics. It also gives an excellent overview of RAW, JPEG and TIFF images, and explains why and under what circumstances would you want to shoot RAW pictures versus ones in JPEG format.