As requested, here is a quick article explaining the use of the en (–) and em (—) dash.

The en dash was named after the letter N because its length is the same as the typeface for that letter. One of the most common ways the en dash is used is to indicate span between items, such as dates, page numbers, and other things that can be listed in consecutive order.

Examples:

For today's lesson, please read pages 257–292 from Writing Today.

This year's rally will be held March 20th–23rd.

Join us Friday–Sunday for food, music, and games.

Each student will be given thirty minutes to complete test sections A–F.

Note: It is incorrect to use an en dash if words are already being used to indicate a span.

Incorrect: Class will be canceled through April 24th–26th.

In the incorrect sentence, the word through and the en dash are trying to do the same job. The en dash can be used when using words to describe a span would be clunky.

Correct: Class will be canceled April 24th through April 26th.

Correct: Class will be canceled April 24th–26th.

The en dash can also be used to show direction, connect names, and compare scores for things like sports and votes.

Examples:

The suspect was last seen boarding a Minneapolis–Seattle bus two weeks ago.

The Vikings defeated the Packers 12–0 last Sunday.

The council decided purple is better than blue after a 6–3 vote on Tuesday.

Today we will study the Briggs–Rauscher reaction.

Note: When connecting two parts of a hyphenated surname use a hyphen (-), not an en (–) dash.

Example: My name is Mary Johnson-Smith.

Like the en dash, the em dash is named after the letter M, and its length matches the width of the M's typeface. The em dash is a very versatile piece of punctuation and can be used in place of commas, parentheses, and colons. It can also be used in dialogue to represent the speaker being interrupted.

Comma example:
Larry put on his shoes—a dirty pair of leather boots—and took one last look at the empty encampment.

Parentheses example:
The em dash—as you've been told—is a very versatile punctuation mark.

Colon example:
Sasha knew Larry cared about one thing, and one thing only—himself.

Dialogue interruption:
Jenny grabbed the map and held it out for Sasha. "This doesn't make any sense at all. The guard tower is on the south side and—"

"You're looking at it upside down. That's why it doesn't make sense," Sasha said as she took the map from Jenny.

Now that you've had a crash course on how to use the en and em dash, you're probably wondering how to add them into your documents. Most word processors will automatically change two consecutive hyphens into an em dash. You can also add them using the insert symbol option in your word processor's toolbar.

If you are a mobile user, chances are you can find them built into your device's keyboard. The en and em dash are usually found when hold down the hyphen button. If your default keyboard doesn't have an em and en dash option—like mine—you can download Grammarly's mobile keyboard app for free. This keyboard does include a hyphen/em/en button; I installed it to make this article.

* Article by glitterandasphalt