Indexed color image

indexed color image:
Images that contain several colors or levels of gray and a palette (or color map) that specifies the color of each given level.
interpolation: ...

Indexed color image. An image with 256 different colors, as opposed to a grayscale image, which has 256 different shades of the tones between black and white.

An indexed color image is based on a palette of, at most, 256 colors. When you convert an image to indexed color, you create a color lookup table, which stores and indexes the colors in the image.
indexed color ...

For a colored pixel in GIMP, these components are usually Red, Green, Blue and sometimes transparency (Alpha). For a Grayscale image, they are Gray and Alpha and for an Indexed color image, they are Indexed and Alpha. ...

See also: Space, Light, Pixels, Stand, Automatic