I think I get it, but I am unsure how to explain. Consider in English: which would you be more likely to ask someone?
"What kind of ice cream is this you are eating?"
"What kind of ice cream are you eating?"
It is implied that you mean "this" ice cream, even without saying "this". And the same for the Russian sentence with это. At least I believe so.
I you want to hear 6 different ways Russians say it, listen to this: https://forvo.com/word/%D0%BC%D0%BE%D1%80%D0%BE%D0%B6%D0%B5%D0%BD%D0%BE%D0%B5/#ru