"The cooks have a big kitchen."
Translation:A szakácsoknak van egy nagy konyhájuk.
To illustrate the difference, consider these questions:
Q: Does János have a hat?
A: János has a hat - "Jánosnak van egy sapkája."
Q: What does János have?
A: A hat. János has a hat. - "Jánosnak sapkája van." - What János has is a hat.
That is the main difference. In "Jánosnak van egy sapkája", János has something. Emphasis on János. In "Jánosnak sapkája van", a hat is what János has. Emphasis on the hat.
It's a shame they don't use some simple extra markup to indicate where the emphasis is. Like "János has a hat", or something. That way you could also be asked to say where the emphasis is, when translating back.
Without that, it's just frustrating until they've consistently added both versions as accepted translations in every sentence. And once they have done that, duolingo will still be unable to teach what the distinction actually is, since it will appear to learners that duolingo is regarding them as interchangeable.
A markup like that would be really helpful, I think. But I guess Duo builds on the foundation that a sentence can be translated however you deem it fit. In that case we can't do much but to wait until the moderators add the remaning sentences, which they've done increasingly sporadically lately. (Woo, three adverbs in a row!)
Duo isn't exactly a proper language teaching service, but rather only gives translation practice. On the contrary, there is a lot of discussion and explanation going on in the comments and interested learners are most welcome to read them and ask questions themselves. The people in the courses I've encountered are really helpful with answering if there are any problems. :)