> I'm not sure what "distributed" means here? Any app in most languages can be coded to be "distributed" both on the scale of within a single machine and at the scale of deploying multiple small instances of it. (eg Kubernetes, running it on multiple EC2s etc etc) The BEAM has a bunch of the "distributed" bits baked in that you then (mostly) don't have to think about when writing your program. If you have two machines, A and B, your program can run on those machines as if it was conceptually a single machine. This is somewhat different from most "distributed" applications.
In general, I find a lot of the patterns around fault tolerance and concurrency to be conceptually easier to work with than languages like Java, C++, etc.
For instance, in Elixir, you might structure a connection to your database as a supervisor and a pool of 10 connections. If something happens to corrupt one of those connections, the process will simply die, the supervisor will see that the process died and spin up a new one to replace it and then re-run any pending queries the dead process was in charge of. You can still handle known exceptions in the process, etc, but the idea is to quickly get back to a good state. The runtime was originally built for managing phone connections so this design choice makes sense.
In terms of concurrency, I find the actor model (which other languages use too!) simpler to reason about vs a process forking model like in Ruby. Essentially, similar to Go, you get parallelism by composing concurrent functions. Unlike Go, however, the composition is at a module level rather than within individual functions. So each function in Elixir/Erlang runs in series, but you can compose modules together to run concurrently and pass messages back and forth.
In general, I would think about Elixir as a Ruby/Node/Python competitor rather than a Java/Rust/C++ competitor. You can very quickly build scalable web applications without a ton of code. My pitch for Phoenix is that it's essentially Rails but built 10 years later; so it has 10 years of learnings (+ solid concurrency support) but doesn't have 10 years of maintenance baggage.
I wrote this very quickly so it's possible some bits aren't clear/precise/etc and I would be happy to elaborate/clarify on some points later when I have time. But hopefully this was helpful. I would also endorse many of the links others have posted if you are interested in more details! Especially the YouTube talk and the Armstrong paper.