Slide 46 doesn't clarify Subjects

So, you can send events TO them, and all their subscribers receive their events. This reads a little confusingly. It's better to say 'They can listen to events they subscribe to and they can broadcast their own events'.

They’re like radios. Lots of people can broadcast on the same frequency, and anyone listening in, gets everything they’re saying. No, what you described is an observable.

This is clearer: http://reactivex.io/documentation/subject.html