The Google Duplex is here, but how does it work?

Google announced a brand new capability of Google Assistant, called Google Duplex. The first thing you’d probably notice in it would be the fluency of the Artificial Intelligence. The change in pitch sounds natural, and so does the super casual “mhmmm”
The Duplex will be used for very limited and controlled conversations, at least for now, because it has to be deeply “trained”, by using the data it collects. But the prospects it holds for the future are pretty exciting.