The dreaded semicolon;

Confession: I still have no idea what the semicolon is for. I am fairly new in my writing journey, and though I remember my adjectives and verbs, I have no memory of learning about the semicolon. In fact I don't think I've ever read a sentence with one in. (Are there any in the Harry Potter series?)

I've turned to google but have been left feeling very unsatisfied. Are we still using them in the days of LOL and emojis? If so.... what purpose do they serve?