In Elixir, a process is a lightweight unit of computation managed by the BEAM VM, while a thread is an OS-level construct. Elixir processes are isolated and communicate via message passing, allowing for efficient concurrency.

Understanding the difference between processes and threads is crucial for effective programming in Elixir. In Elixir, a process is a lightweight, isolated unit of computation managed by the BEAM virtual machine. Each Elixir process has its own state and memory space, meaning that they cannot directly access each other's state, which promotes safety and avoids common concurrency issues such as race conditions. Communication between processes occurs through message passing, where one process sends messages to another's process identifier (PID). This model allows for highly concurrent applications, as thousands of processes can be spawned without the overhead typically associated with OS-level threads. In contrast, threads are managed by the operating system and can share memory, leading to potential conflicts if not handled carefully. While Elixir abstracts away many of the complexities associated with traditional threading models, it's essential to understand these differences to leverage the power of Elixir's concurrency model effectively. By using lightweight processes instead of threads, Elixir enables developers to create robust and scalable applications while minimizing the risks associated with shared state.