Why do you need to choose (or tell the worker) “credit” or “debit” when paying for something by card? Are the two cards built differently?

Question

Why do you need to choose (or tell the worker) “credit” or “debit” when paying for something by card? Are the two cards built differently?

In: Other

Answer 1

Also, for other people: In Canada – even in Vancouver – some card machines DOES require you to specify whether you are using debit or credit. I recall some Timmies and 7-11 does that.