Man, writing is hard.
Self: en dash is the short dash. It’s used for closed range things and for linking things together.
An em dash is the long dash. Quoting from the wiki:
The em dash indicates a sudden break in thoughtâ€”a parenthetical statement like this oneâ€”or an open range (such as “John Doe, 1987â€””). The em dash is used in much the way a colon or set of parentheses is used: it can show an abrupt change in thought or be used where a period is too strong and a comma too weak. Em dashes are sometimes used in lists or definitions, but this is not considered correct usage[citationÂ needed]: a colon should be used instead.