Grammarly
Grammarly Blog: Dashes
This page focuses on the rules for the use of dashes. Explains what a dash is, what it does, and the three formats of dashes (em, en, and the double hyphen). Examples are provided with the "dash" used in different contexts.
Sophia Learning
Sophia: Dashes and Hyphens: Lesson 1
This lesson introduces hyphens and dashes. It explains the hyphen, en dash, em dash, and dash and the uses of each. It is 1 of 4 in the series titled "Dashes and Hyphens." L.11-12.2a Hyphens