GrammarSam, AKA Sam Beeson, takes a break from his school classroom to help us sort out the hyphen and dash.
Hyphens connect things. They are used when writing something like 112-page document or mother-in-law. There are no spaces between the words and the hyphen.
2. En dash
Dashes separate things. Named after the actual width of the letter n, this dash is used when indicating the meaning “to” — as in this example: “From 1971 – 1990, Grammar Sam’s parents were in a rock band called 5th Avenue.”
3. Em dash
Again, dash separate things. Named after the actual width of the letter m, this is used like parentheses—a good stylistic idea sometimes—and it is formatted by leaving no space between the last letter of the preceding word and the first letter of the following word.