Elixir runs on the Erlang Virtual Machine (BEAM). The BEAM is a virtual machine specifically designed for executing Erlang and Elixir code. It provides a runtime environment that manages processes, handles concurrency, and offers fault tolerance and distribution capabilities.

The choice of the BEAM as the platform for Elixir brings several advantages. Here are a few:

* Concurrency and Parallelism : The BEAM is built to handle massive concurrency. It utilizes lightweight processes, known as Erlang processes, which are independent units of execution that communicate through message passing. This enables Elixir to efficiently handle thousands or even millions of concurrent processes, making it well-suited for building scalable and highly concurrent applications.

* Fault Tolerance : The BEAM has built-in mechanisms for handling errors and failures. It follows the "Let it crash" philosophy, where individual processes are allowed to fail, but the system as a whole remains resilient. Supervision trees in Elixir/OTP (Open Telecom Platform) provide a way to monitor and restart failed processes, ensuring the overall system's fault tolerance.

* Distributed Computing : The BEAM provides excellent support for building distributed systems. Elixir/Erlang nodes can seamlessly communicate with each other across different machines, forming a distributed network. This allows for building fault-tolerant and highly available systems that span multiple nodes.

* Interoperability : Elixir is fully compatible with Erlang. It can leverage existing Erlang libraries and systems, making it easy to reuse code and access the rich ecosystem of Erlang/OTP. Elixir code can call Erlang functions directly, and vice versa, enabling integration with a wide range of existing systems.

* Hot Code Swapping : The BEAM supports hot code swapping, which allows applications to be upgraded or modified while they are running without stopping or restarting the system. This feature facilitates zero-downtime upgrades and enables systems to evolve and adapt dynamically.