There are 3 lengths of dashes: the shortest is the hypen (-), then the n-dash (–), and the longest is the m-dash (—).
The hyphen is used to join things together: so-called, buttermilk-fed, A-Team, 604-555-1323, #206 – 3245 W. 2nd.
The n-dash is used to indicate a range: 1–5, 3244–3245 W. 2nd, 1963–67, fifth–sixth.
The m-dash keeps things apart—like this.
“I told him it was pretty extreme—obscene acutally—these 5–6 buttermilk-fed poodle-huskies. He claims that in 2002–3 there will be a voracious craze for fat, curly-haired sled-dogs—but I think he’s nuts. He claims to own a townhouse that covers the fifth–sixth floors at 320 – 27th Street. I don’t believe him—but I gave him our phone number anyway (604-555-1323), because he might need a brochure or website someday.”