Linux users should try vi in a terminal;

$ vi        (now type in the vi command ":help 42")

<esc>
:
h
e
l
p
 
4
2
<Enter>

         (And you may need to know how to gracefully quit)

<esc>
:
q
<Enter>

$

The escape-colon sequence is a toggle between command line mode and edit mode.
Personally I've always felt that vi came from another galaxy... and I press <insert> once to begin every edit.

  (-:  Chas.M.  :-)