Em dash, I loathe your very existence. What are you anyway? Nothing more than an advanced dash in my mind. I hear you snicker everytime I forget how to create you in Quark. Wikipedia explains you as thus:
The em dash (—), or m dash, m-rule, etc., often demarcates a parenthetical thought—like this one—or some similar interpolation. It is also used to indicate that a sentence is unfinished because the speaker has been interrupted.Whatever. Die em dash. Your purpose matters not.