Elixir is good for fault tolerance, high concurrency, and distribution. It is built on Erlang and shares Erlang's strengths like robustness and distribution. Elixir brings Erlang's strengths with a syntax inspired by Ruby and Clojure, making it more approachable. Key features include immutable data structures, pattern matching, pipe operators, metaprogramming with macros, lightweight processes and message passing, and the OTP framework for building fault-tolerant systems. Popular companies like WhatsApp and RabbitMQ use Elixir for its robustness in handling large numbers of concurrent connections.