Actors are inherently stateful, they provide safe encapsulation coupled with patterns for persistence (see https://github.com/eligosource/eventsourced for example). Other properties are that they have addresses (ActorRef in Akka) which support location transparency, meaning that every actor which has another actor’s ActorRef can send it a message, no matter whether within the same JVM or across the network. Akka’s particular strength is that it enforces actor supervision, making your software design resilient (see http://www.infoq.com/articles/resilient-software-with-akka).