What is the difference between ale, bitter, lager and stout?

What is the difference between ale, bitter, lager and stout? I often get this and similar questions.

Here is the short answer and definition I have come up with:

• Ale
  Made with a top fermenting yeast, ales are described as hearty, robust, and fruity.
• Bitter
  A mainstay in English pubs, this golden-brown draft ale is top-fermented, hoppy, dry, and lightly carbonated.
• Lager
  Made with a bottom fermenting yeast, lagers are characteristically smooth, elegant, crisp, and clean. Comparable to pilsener.
• Stout
  Typically dark, heavy, and richly flavored, stout is top-fermented beer made from pale malt, roasted unmalted barley, and often caramel malt.