I think the real killer feature of Elixir is that it is a friendly, Ruby-like language that gives you access to the underlying power of Erlang/OTP on the Beam VM.
OTP (Open Telecom Platform) is a set of tools, libraries, and middleware that was built around Erlang. This has been in development since the 90s, and was originally developed by Ericsson for the telecom industry to handle massive numbers of concurrent connections without a single point of failure (I may be butchering this story, but this was the end result). OTP includes things like extremely lightweight processes, process supervision to quickly restart based on your desired behavior, multiple native real-time datastore options (both in-memory and/or persistent), hot deployments with no downtime, an extensive standard library, and other cool things that have stood the test of time. All of this just comes with the base Erlang/OTP installation.
Elixir essentially introduces a modern ecosystem around the Erlang/OTP system.
True in a lot of cases. However, Phoenix has major similarities to Ruby on Rails, and Elixir is often the functional language of choice for those moving away from RoR.
OTP (Open Telecom Platform) is a set of tools, libraries, and middleware that was built around Erlang. This has been in development since the 90s, and was originally developed by Ericsson for the telecom industry to handle massive numbers of concurrent connections without a single point of failure (I may be butchering this story, but this was the end result). OTP includes things like extremely lightweight processes, process supervision to quickly restart based on your desired behavior, multiple native real-time datastore options (both in-memory and/or persistent), hot deployments with no downtime, an extensive standard library, and other cool things that have stood the test of time. All of this just comes with the base Erlang/OTP installation.
Elixir essentially introduces a modern ecosystem around the Erlang/OTP system.