Besides the LaTeX use, on Linux if you have gone into your keyboard options and configured a rarely-used key to be your Compose key (I like to use the "menu" key for this purpose, or right Alt if on a keyboard with no "menu" key), you can type Compose sequences as follows (note how they closely resemble the LaTeX -- or --- sequences):

Compose, hyphen, hyphen, period: produces – (en dash) Compose, hyphen, hyphen, hyphen: produces — (em dash)

And many other useful sequences too, like Compose, lowercase o, lowercase o to produce the ° (degree) symbol. If you're running Linux, look into your keyboard settings and dig into the advanced settings until you find the Compose key, it's super handy.

P.S. If I was running Windows I would probably never type em dashes. But since the key combination to type them on Linux is so easy to remember, I use em dashes, degree symbols, and other things all the time.