"Is a tomato a vegetable?"
Translation:Czy pomidor to warzywo?
So, if I even understand it correctly, technically "jarzyna" is an edible part of a root crop and it can be eaten raw. So only some vegetables would undergo this definition. But this difference in meaning is vanishing, so "jarzyna" is often considered a synonym.
We accept "jarzyna", but personally I'd advise to just keep to "warzywo". It's good to know what "jarzyna" means, but you don't have to use it.
Yes. "To" has many uses, one of which is "this" as an adjective for neuter nouns, another as a sort of noun substitute meaning "this thing here", and finally as a verb substitute meaning "is".
Unlike "jest" (which requires Instrumental), "to" takes the Nominative.