Akka documentation simply explains an ActorSystem as a heavyweight structure that will allocate 1 to N threads, and we should create one per logical application. Once we create an actor system, we get the license to create actors under that system. We'll take a look at how we can create Actors in the next sections.
When we create actors as part of a system, these actors share the same configuration (such as dispatchers, paths, and addresses) as the Actor system.
Within an Actor system, there's a root guardian Actor; this serves as a parent actor to all actors residing within an actor system, internal actors, as well actors that we create. So, as expected, this is the last actor to be stopped when the system terminates.
The reason why Akka provides these guardian actors is to supervise the first-level actors we create, so...