The other answers have covered the technical details well, but not so much the philosophical ones. You may have heard about how Erlang with the BEAM is a fanta

The other answers have covered the technical details well, but not so much the philosophical ones. You may have heard about how Erlang with the BEAM is a fantastic implementation of the Actor programming model. This involves lots of processes (green threads) holding a little bit of state and communicating with messages. It's both a great concurrency model and a great programming model. The standard library (OTP) then also provides excellent tools for managing these processes in supervision trees. Ports act like another actor in a supervision tree. This actor happens to be a C program and the messages are sent and received by stdout/stdin, but otherwise it behaves like a process. You can manage its runtime state with supervision trees and all the other excellent tools that BEAM/OTP give you. NIFs on the other hand are best used to replace something that could be a pure function in Erlang, but is a lot faster in something compiled (or because you want to leverage some existing codebase that does that).