Use for simple images on the web. Popular in the FAX world, and with scanners. There is no colour compression, so this is the format of choice for maximum information fidelity. The penalty is greater file size. JPEG - Good for photographic images, bad for line art and object graphics.
Colour depth is enormous.
JPEG is not good or efficient with large blocks of single colours or with text. You choose the degree of compression according to how much quality you can afford to lose. Use for photographic images on the web. RGB - A misleading name used by SGI for their uncompressed pixmapped images. No compression, no loss, no space left on disk.