Parallel Virtual Machine (PVM) is a software tool that enables a group of computers to work together as a single, powerful virtual machine. It allows users to write programs that can run on multiple machines simultaneously, improving performance for complex computations. PVM is particularly useful in high-performance computing environments where tasks can be divided among several processors. PVM operates by managing the communication and coordination between the different machines involved in the computation. It provides a set of programming interfaces that allow developers to easily send and receive messages between processes, facilitating parallel processing. This makes it easier to develop applications that can efficiently utilize distributed computing resources.