If we were using a different sentence, for example, Det här bröd är grekiskt, then there is absolutely no difference in meaning whatsoever. The English phrases "This bread is Greek" and "This is Greek bread" are 100% interchangeable. The latter is BY FAR the most natural sounding one for native English speakers.
The confusion in this particular sentence comes from the fact that "French bread" is a specific thing. In the same vein, "This is French toast" does not mean the same as "This toast is French."
They are 100% interchangeable when there is no context.
If someone asked me "What is this?" I would answer with "It's French bread" or "It's Greek bread." I don't think I would ever use the word "this" in my answer. When I see a sentence start with "This is ..." I do not think of it as an answer to a question.
You will be frustrated constantly with this course if you try to use any context-free translation you like. You generally have to try to match the sentence as closely as you can if there are two alternatives, and use your imagination to come up with a situation in which that one would be preferred over the other. This allows the course to teach more, which you grow to appreciate over time. For example, even when two forms are interchangeable, the fact that both forms exist in both languages is useful to know. If it marks you right for something that has another more direct translation, it's not teaching you that. You will enjoy the course more if you accept that as part of its underlying approach.
The best I can think of is that, in colloquial English, "French bread" is a specific thing: a baguette. Thus, if I were serving a Pain Poilane, I might actually say "this bread is French" to clarify that I am not talking about a baguette, but rather a different variety of bread from France.
Swedish uses words like franskbröd and långfranska to refer to the thing we call "French bread."
The fact that this sentence example does not use franskbröd or långfranska is a good indication that using the English "French bread" would be incorrect.
I agree, however, that "this bread is French" would be a very unusual thing to say in English. It is 100% NOT what anyone would ever say while pointing at a baguette. It would only be something said while pointing at another variety of bread from France.
This is where Duolingo might benefit from pictures to provide some sense of context.
I agree. I'm English. I don't understand 'aranworld's' response. Plus, I have no idea that in Sweden 'franskbröd' exists so it's a pain to have to guess that. Even if I did, I would only use 'this bread is French' in a sentence distinguishing two things 'This bread is Swedish bread and this bread is Italian'. Why I would ever need that sentence, I have no idea, but can see the grammar is useful for other contexts. But, in this instance it is too much of a fragment to make sense.
The noun always goes definite when you use den här, det här, de här. It's just one of the rules of the grammar. (But it doesn't happen, in written form, with the alternative equivalents denna, detta, dessa. See https://www.duolingo.com/skill/sv/Determiners .)
It also happens when an adjective takes the place of här too (and incidentally, the adjective goes into its definite form, which is the same as the "plural" form): e.g. det vita brödet (cf. vitt bröd).
Maybe a bit offtopic but noticed when I get an answer wrong the question directly repeated. In earlier versions the wrongly answered question are repeated at the end. The old method works much better because now you just try one of the other answers instead of trying to remember/decipher the actual words and their meaning. Please revert this change or create a setting so other people who don't agree can use the current method.