A lot of people aren’t aware what an en-dash or em-dash is, let alone how to use them. Unlike apostrophes and semi-colons, misusing them won’t affect the flow or meaning of a sentence. That being said, there is a difference and it’s important to learn it to avoid schoolboy errors.
A hyphen is what’s used to link two words, hence hyphenate. It’s the short dash that we see quite often, such as ‘semi-colons’ above. An en-dash looks like a longer dash and is used to replace ‘to’ when mentioning periods of time, like January–December, 1990–1991, 9–5 etc. An em-dash is what you see when a dash pops up mid-sentence, such as “no one – and I mean no one – has ever done that”
Microsoft Word will generally create an em-dash for you, if you put a hyphen in followed by a space and a word, the hyphen will change to an em-dash. If not, on a standard PC keyboard, ctrl+hyphen should generate one.