What's a Cassette

A couple of weeks ago we were driving somewhere, maybe Kohls, maybe Walmart, I forget exactly.  But were were driving in my car and had the satellite radio on.  I was flipping stations and landed on the hair band channel.  I don't remember exactly what was on but it was a song that I hadn't heard in years.  I know it was something that Kris liked too.  I said something about how I remembered having the album by whoever it was on cassette back when I was in high school.  Alison was sitting in the backseat and asked, "What's a cassette?"  My mouth dropped open, and I said, "What? Are you kidding?"  I thought for certain she was putting us on, but she was serious.  Apparently she had never seen a cassette tape before.  That was how I knew I was officially old