Erlang is a general-purpose concurrent, garbage-collected
programming language and runtime system. The sequential subset
of Erlang is a functional language, with strict evaluation,
single assignment, and dynamic typing. For concurrency it
follows the Actor model.
In computer science, the Actor model is a mathematical model of
concurrent computation that treats "actors" as the universal
primitives of concurrent digital computation: in response to a
message that it receives, an actor can make local decisions,
create more actors, send more messages, and determine how to
respond to the next message received.
http://lstephen.wordpress.com/2007/09/08/the-actors-model-and-haskell/