Punctuation marks are like road signs for readers. They guide the eye, signaling whether one needs to stop (a period), pause (a comma), watch for a shift in focus (an em-dash), notice a connection (hyphens and en-dashes), and more.
For whatever reason, people seem to have more trouble with the semicolon and colons than the others.
Not necessarily with where to place them (that’s a comma problem, always, and it’s job security for us copyeditors), but when to use them at all.
Today, I’m hoping to shed light on the mysteries of these two marks.