MPICH is an open-source implementation of the Message Passing Interface (MPI) standard, which is widely used for parallel programming in high-performance computing. It allows multiple processes to communicate with each other, enabling efficient execution of complex computations across distributed systems. Developed at Argonne National Laboratory, MPICH is designed to be portable and scalable, making it suitable for various computing environments, from small clusters to large supercomputers. Its modular architecture supports different network protocols, enhancing performance and flexibility for developers and researchers working on parallel applications.