What is an en dash vs an em dash?
From shortest to longest, the hierarchy of dashes would be as follows: hyphen, en dash, em dash.
The hyphen is used to connect words that function together to create a joint concept, such as "editor-in-chief" or "last-minute".
The en-dash is used to cite a range, such as "May–September" or "pages 130–150", or to connect a prefix to another word or phrase: "post–antebellum".
The em-dash is often used in place of parentheses to designate an additional phrase in a sentence: "Since 2007, the consensus of the economic establishment—bankers, policymakers, CEOs, stock analysts, pundits—has been catastrophically wrong. [Slate]"