NMT models?

Under Creating translation engines, we are told that "Before you begin: Make sure you created and defined NMT Models." But the link leads nowhere, and I can't figure out what NMT models really are. When I select Resources > Manchine Translation Engines > NMT Models, I get a long list of "Neural Machine Translation Models" which I certainly have neither created nor defined. And why they are called models I can't understand. They are all generic anyway.

So maybe someone can explain this "creating and defining" matter?