I know the difference between an em dash and hyphen. I just get em dash and en dash mixed up, but thought I'd look it up again, in case anyone cares.

From Scribbr:

The en dash is approximately the length of the letter N, and the em dash the length of the letter M. The shorter en dash (–) is used to mark ranges and with the meaning “to” in phrases like “Dover–Calais crossing.” The longer em dash (—) is used to separate extra information or mark a break in a sentence.

There you have it, Chrys O'Shea - Writing again.