Address identifies an actor. However, it may also represent a proxy/forwarder to an actor(e.g. a load balancer). The addresses contain location(e.g. IP addresses) and transportation information(e.g. TCP/UDP). They give us the notion of location transparency. As a programmer, we don't need to care about where the actor lives, as long as we can send message to it. In other words, we can have actors in the same process, or different machines, but how you communicate are completely the same across all of them.