Comment by Jaruzel

Ok, so...

Linux Newbie:

"I need to find out how much space I have left on this machine."

  > freespace
  bash: freespace: command not found
  > diskspace
  bash: diskspace: command not found
  > disk info
  bash: disk: command not found
  > diskinfo
  bash: diskinfo: command not found
  > man disk space
  No manual entry for disk
  No manual entry for space
  > help disk space
  bash: help: no help topics match `space'.  Try `help help' or `man -k space' or `info space'.

(looks it up on the internet)

  > df /dev/sda1
  Filesystem     1K-blocks    Used Available Use% Mounted on
  /dev/sda1       19478160 1370768  17094912   8% /

... AND that's why GUIs are preferred by most non-technical computer users.

EDIT: Maybe I should have said 'CLI Newbie' - I am in no-way singling out Linux here.