Pixel

Pixels are light receptors on a digital camera sensor. Think of them as buckets for light reaching the sensor. Each bucket records the amount of light reaching it and when assembled into an image, we see brighter areas where more light was gathered in the pixels and darker areas where little light was gathered by the pixels. Sensors have multiple layers of pixels tightly packed together for gather specific colors: Red, Green, and Blue. By mixing the colors of each specific light color gathered, virtually any other color can be formed.

A 8 megapixel camera has 8 million pixels on the sensor.

In choosing a camera, you will want enough megapixels to cover the largest print you might ever make. Give some consideration to cropping as well. An image with 300 pixels per inch is considered high quality; however, dropping below 120 pixels per inch is low quality. An 8"x10" image will need 2400x3000 pixels for a high quality image, and that is a total of 7.2 megapixels.

For internet-only displaying, an image of 900x1200 pixels will fill many monitors screens. That is only 1.1 megapixels. A high quality 3"x4" print can be made, or a low quality 8"x10" print.

Post-processing can easily reduce the number of pixels shown in the final image, but adding pixels generally will make a less attractive image.