Hyphens, en and em dashes appear with great frequency in typeset copy. Unlike the days of typewriters where the only character available to represent these three punctuation marks was a hyphen, all three are available in almost all of today’s fonts. They all have different usages, most of which are a mystery to us designer types. Extensis Blogger, Ilene Strizver, has a great article that explains what Hyphens, En and Em Dashes are and when you should use them.
We all know the Hyphen is made by simply hitting the dash key in the number row on your keyboard. An En Dash is made by hitting Option + dash key. The Em Dash is made via Shift + Option + dash key.