What are the Meta, Super, and Hyper keys in Linux/Unix?

Meta, Super and Hyper keys are referenced most often in various Linux Distros but many users are unaware what these really are.So let me explain each -

•  Meta :
  The Meta key is not found on modern keyboard, it's use is sometimes emulated with AltGr (on some international layouts) or the right Alt key on the others. In addition:
  1. Sun keyboards have a meta key (◆) as well
  2. Emacs calls Esc the Meta key
•  Super :
  The Super key is equivalent to or the ⌘ (command) key. In Ubuntu, it's just another name for .
• Hyper :
  Hyper is the fourth (counting Ctrl) and last modifier on the Space cadet keyboard. In Ubuntu, its function is undefined (I think), but it can be mapped, as in the screen shot above, to , should it be needed

Though above are default setting you can change the mappings.
I am using Ubuntu 12.04 LTS and in this we can change this mapping from

System Settings -> Keyboard Layout -> options -> Alt/Win key behavior.