An almost trivial example of PubSub is the daily newspaper:
Once you have a subscription, you automatically get each new publication.
Typically, you are not the only subscriber; the same ‘newspaper’ is sent to all subscribers: everybody got his
copy. And, whenever somebody cancels his subscription, all others still get there update daily.
Also notice: your copy is independent of that the neighbors. And, until you subscribe, the publisher does not know you.
In software-engineering, we call that uncoupled or loosely coupled, and that is great.
As we will explain in the next page.