What is the difference between typing `emacs-x` and `emacs`?

"Under debian I have:

% ls -l /usr/bin/emacs
lrwxrwxrwx 1 root root 23 25 sept. 2009 /usr/bin/emacs -> /etc/alternatives/emacs
% ls -l /etc/alternatives/emacs
lrwxrwxrwx 1 root root 18 25 sept. 2009 /etc/alternatives/emacs -> /usr/bin/emacs23-x

showing that emacs is realy emacs23-x. Probably, on your system, you will see that emacs is realy emacs-x. The use of symlink give the opportunity to the admin of your box to choose which Emacs is the default one, and the presence of the others executable enable the users of your box to choose which of the installed Emacs they want to run."