Where does the iot_session come from?

[liteon-andrew-ho]

I'm following the steps in the document to build iot-sample in Omniverse Composer. However, when I came to the section Joining a Live Session, I wondered where does the iot_session come from?
On the other hand, I'd like to know what controls the movement of the cube and those roller prim, because it seems that without the extension and the run_app.py, the cube and roller can still move.