Drawing its name from PIX [picture] and El [Element], a pixel is the smallest unit used to create an image on a device such as a computer screen. The resolution of a graphics device, like a monitor, display, scanner, digital camera, etc., is measured in pixels. The higher the pixel resolution (the more rows and columns of pixels), the more information can be displayed. The term megapixel is used to refer to a resolution of over a million pixels.

On your screen, pixels are made up of one or more dots of color. Monochrome and gray scale systems use one dot per pixel. Color systems use three colorful dots per pixel; red, green, and blue. Each dot can be energized to different intensities. A range of colors can be created by mixing these dots. With more pixels on screen, more of the document is visible, but the text and images will appear smaller. 

In digital photography, the number of pixels is the major determinant of picture quality - the more pixels, the larger and clearer the picture is likely to be. It is especially important to note that the higher the resolution of a digital camera, the larger a photograph can be printed and still retain its clarity.