Have you ever tried to explain the Control and Alt keys to a Regular Person? They suddenly seem like the epitome of geekly shortcuts. Well, don’t bother showing them the space cadet keyboard. It came with the Symbolics Lisp Machine, and had not just Shift, Control and Alt modifier keys, but also Top, Greek, Meta, Hyper and Super. They took a standard practice and cranked it up way past eleven, creating a geekutopia for entering data into a computer.
Emacs still retains some of this history. It will let you define variants of keystrokes using modifiers like Meta, Hyper, and Super. There’s more about the keyboard at the Free On-Line Dictionary of Computing