PhotoShop color mode choices

I probably won't include these on this Friday's Photography quiz, but they're important to know if you want to have a quality image with good bit-depth;

• RGB- Red, Green, and Blue, 256 shades of the three main colors, most comon for JPEGs
  
• Indexed colors- locked in to a table of web-frioendly colors, best for GIFs
• CYMK- Cyan, Yellow, Magenta, and blacK, traditional printer's colors (often TIFFs)
• Greyscale- Nice, deep 8 bit black and white, producing a good 256 shades, good old "black and white" photography
• 4 Bit black and white- Maybe a couple of shades of gray plus black and white- looks really graphic like a poster or something.
  
• 2 Bit- ONLY black and white with no in between, what we used to call "line art"