The Actor Model that was introduced in 1973 looks at the world as a set of actors that holds a state and a behavior.
This idea is very similar to OOP that we all know and love, but actors are not limited to a single machine.
Instead, actors can be distributed to multiple processes and machine, and create a network of processors that encapsulate the problem-domain.
This model has significant implications on the way we can write large scale distributed systems and can make very hard problems, very easy to solve.