Concurrency and parallelism are related concepts in the context of concurrent programming, and Erlang provides mechanisms to handle both effectively.

Concurrency refers to the ability of a program to execute multiple tasks or processes concurrently, allowing progress on multiple tasks to overlap in time. In Erlang, concurrency is achieved through the use of lightweight processes, also known as Erlang processes. These processes are independent units of execution that can run concurrently, communicate with each other, and share information through message passing.

Erlang processes are extremely lightweight, and thousands or even millions of processes can be created within an Erlang system. Each process has its own stack, heap, and program counter, allowing them to execute independently and concurrently. Erlang processes are managed by the Erlang virtual machine (BEAM), which efficiently schedules and switches between processes, ensuring fairness and progress for all concurrent tasks. Parallelism, on the other hand, refers to the execution of multiple tasks simultaneously, leveraging multiple computational resources such as multiple CPU cores or machines. Erlang provides support for parallelism through its distributed computing capabilities. With Erlang's distribution features, Erlang processes can be spread across multiple nodes, which can be separate machines or cores within a machine. These distributed processes can communicate with each other seamlessly, enabling parallel execution of tasks across different nodes.

By combining concurrency and parallelism, Erlang allows developers to build highly concurrent and parallel systems. Concurrency allows for the effective utilization of system resources and responsiveness, while parallelism enables scalability and the efficient utilization of multiple computational resources.

Erlang's concurrency and parallelism features are well-suited for building systems that require high availability, fault tolerance, and scalability, such as telecommunication systems, messaging platforms, and distributed applications. The actor model, lightweight processes, and message passing in Erlang provide a powerful and intuitive model for handling concurrency, while the distributed capabilities enable efficient parallel execution across multiple nodes.