How would YOU describe a semicolon?

This morning, one of my students called me over to her desk and showed me a scribble on a page of her notebook.

“Miss Ailey, what called this?” she asked.

“Oh!” I said. “That's a semicolon!”

She looked at me questioningly, which I took as an unvoiced plea for explanation. But how does one explain a semicolon? More importantly, how does one explain a semicolon to someone who's only been studying English for twelve months? I was perplexed. I was flabbergasted. I was embarrassed by the fact that I probably couldn't explain a semicolon to a natural English speaker – and I majored in Creative Writing.

In the few seconds between the student's questioning look and my shaky explanation, I did some deep thinking about the nature of the semicolon. I thought about how creative it was for someone to combine a colon with a comma. I pondered the graceful curve of the semicolon's lower half and how it seemed to beckon the reader on – don't stop here, the best is yet to come! – while warning them to slow down, something new will be revealed on the other side of this punctuation mark. Do you really dare to venture on?

I pointed at a sentence in the student's textbook, “See this? This is a comma. And this? This is a period. A semicolon is somewhere between a comma and a period.” Then I drew a mini graph that looked like this:

, (comma) ---------------- ; (semicolon) --------------------- . (period)

Does it matter that I completely left out the existence of the colon? I don't think the student will notice. But my question is this: How would YOU explain the semicolon?

And why don't I have a better explanation for what it is?