Bits Per Pixel (BPP) determines how many colors are available for any given pixel in an image. For example 8 BPP = 2x2x2x2x2x2x2x2 = 256 colors, like a GIF image. 16 BPP = 2x2x2x2x2x2x2x2x2x2x2x2x2x2x2x2 = 65536 colors.
See also BPC (bits per channel).
