The fault tolerance that I love about Erlang/Elixir is the actor model. Everything is (or can be) an actor, which is like a living and breathing instance of a class. So they can live and do their own stuff, and then if they fail at that and need to be recreated, they get recreated by something that supervises them.

Contrast this to for instance a Django or Rails app... if a vital service in the system dies the entire Ruby or Python runtime will (potentially) die and then respawn. It's cheap and we don't care, right? It will get restarted. The net result is similar, you don't get woken up in the middle of the night and customers are happy. But in systems where you want or NEED an entire system to remain on 24x7x365 it changes the game.