Comment by strogonoff

For a somewhat more advanced (and IMHO much more beautifully typeset) but still succinct overview of em dash (and some other dashes) in practical use, see https://twos.dev/dashes.html.

Suitable for those who are familiar with punctuation basics but may want a refresher, and AFAICT gets some things more correctly (e.g., the numbers in a range are generally separated by a figure dash, not en dash).