OTP (Open Telecom Platform) is a set of libraries, design principles, and tools that provide a framework for building reliable, fault-tolerant, and scalable systems in Elixir (and Erlang). OTP is not specific to Elixir but is widely used in Elixir development due to its seamless integration with the language.

Here are the key components and concepts of OTP:

* Supervisors : OTP introduces the concept of supervisors, which are processes responsible for monitoring and managing other processes, known as workers. Supervisors are defined using a hierarchical structure called a supervision tree. If a worker process crashes, the supervisor can automatically restart it, maintaining the overall system's stability and availability.

* Behaviors : OTP provides predefined behaviors, which are generic implementations of common patterns for building processes and systems. These behaviors include `GenServer`, `GenEvent`, `GenStateMachine`, and more. Behaviors encapsulate the boilerplate code required for implementing specific process types, such as handling messages, state management, event handling, and error recovery.

* Applications : In OTP, an application is a logical unit that groups related components together. It represents a part of the system with its own supervision tree, configuration, and dependencies. Applications provide a modular and manageable way to organize and deploy Elixir/Erlang systems. * Release Management : OTP includes tools and mechanisms for managing the deployment of applications. A release is a self-contained package that includes all the necessary components and resources for running an application. OTP provides tools like `mix release` and `exrm` to generate releases, allowing for easy distribution and deployment of Elixir/Erlang applications.

* OTP Libraries : OTP comes with a set of standard libraries that provide functionality for common tasks in distributed systems, including distributed process communication, fault tolerance, distributed data storage, and more. These libraries, such as `OTP.Registry`, `OTP.Supervisor`, `OTP.Application`, and `OTP.GenServer`, form the foundation of building scalable and fault-tolerant applications in Elixir.

* Hot Code Swapping : One of the notable features of OTP is its ability to perform hot code swapping. Hot code swapping allows applications to be upgraded or modified while they are running, without any downtime or interruption. This feature is particularly useful for systems that require continuous availability and need to evolve and adapt dynamically.