from the man page:

       This  program  puts  your  terminal  in  raw mode, eats keystrokes, and
       prints them back it you in a recognizable printed form  (using  <>-sur-
       rounded ASCII mnemonics for non-printables).

       This  may  be useful, for example, if you're not certain what your key-
       board keys are sending.

WWW:  http://catb.org/~esr/showkey/