Concurrency is of course a whole different animal. It has nothing to do with functional programming but since Erlang is a functional programming language that supports concurrency we can continue with Elixir. Different language have different ways of handling concurrency and especially how concurrent processes communicate. Elixir implements a model called actors model where processes communicate by messages, this model is also found in Scala and Go.
After the lecture
Take a look at the exercises related to concurrency.