Basically only message passing. As another poited out, you can use FFI calls and Erlang Term Storage, possibly some other means to communicate, but the central

Basically only message passing. As another poited out, you can use FFI calls and Erlang Term Storage, possibly some other means to communicate, but the central feature is that each process has an ID, and then you send() a message to it. each process also has a receive() block where you essentially listen to everything that ends up in your mailbox and pattern match on it to take action.