There are commands that switch you into input mode.
  There is only one key that takes you out of input mode,
  and that is the <escape> key. (Key names are written
  using less-than and greater-than signs, e.g. <escape>
  means the ``escape'' key, usually labeled ``esc'' on
  your terminal's keyboard.)  If you're	ever confused 
  as to which mode you're in, keep entering the <escape>
  key until vi beeps at you.