A pixel (from the words pix, for picture, and element) is the smallest element on a video display screen. A screen contains thousands of pixels, each of which can be made up of one or more dots or a cluster of dots. On a simple monochrome screen, a pixel is one dot; the two colors of image and background are created when the pixel is switched either on or off. Some monochrome screen pixels can be energized to create different light intensities to allow a range of shades from light to dark. On color screens, three dot colors are included in each pixel—red, green, and blue. The simplest screens have just one dot of each color, but more elaborate screens have pixels with clusters of each color. These more elaborate displays can show a large number of colors and intensities. On color screens, black is created by leaving all three colors off; white by all three colors on; and a range of grays by equal intensities of all the colors.

The resolution of a computer monitor is expressed as the number of pixels on the horizontal axis and the number of pixels on the vertical axis, For example, a monitor described as 800×600 has 800 pixels on the horizontal axis and 600 pixels on the vertical axis. The higher the numbers, e.g., 1600 × 1200, the better the resolution.