I've had several clients ask me about hyphens, en-dashes and em-dashes lately, so I wanted to give a quick run-down:
The en-dash usually replaces "to" or "through" between ranges:
Please join us on Saturday, 1:00–9:00, to watch a Star Wars marathon.
New Zealand beat the West Indies in cricket today, 6–0.
The em-dash can be thought of as used in place of a colon, commas, and parentheses:
I have two pets—a tauntaun and a bantha. (Dash used in place of a colon.)
My two pets—a tauntaun and a bantha—are quite rambunctious. (You could replace the dashes with commas or parentheses, but note that dashes shout this extra news, where commas and parentheses whisper it. If you really want your reader to pay attention, use dashes.
Some English publications, such as Penguin, use en-dashes with a space on either side in a similar manner, but others, such as Oxford University Press prefer the closed em-dash, as above. When in doubt, go for closed em-dash, as no one will mistake your intent.)
Use an em-dash to indicate that a speaker has been interrupted:
"Han Solo was going to tell you that—"
The em-dash can also be used to signify an abrupt change in thought.
"I was going to tell you that—hold on, C3PO is at the door."
A hyphen is used to join words in a compound construction, or separate syllables of a word, like during a line break.:
cruelty-free fynock eggs
Finally, just throwing this in the mix, a minus sign − is distinct from all three of the above.
4 − 2 = 2.