It's their job to explain it to you. Most baristas are pretty good at that job. They often love coffee and love talking about coffee.

Everybody behind a tip screen is doing a customer service job. It's not just taking money and giving coffee. It's a hospitality industry. Not everybody is good at it, but a properly-run shop is good at hospitality because they know it's how they make their living.

So really, just ask. I can't promise you that the person behind the counter isn't a jerk, but I suspect you'll be surprised and pleased.