Inter-process communication (IPC) allows parent and child processes in Node.js to exchange data efficiently. When you use the fork() method from the child_process module, Node.js automatically sets up an IPC channel between the parent and child. This channel enables both processes to send and receive messages using the send() method and to listen for messages using the message event.

In the example above, the parent process uses child.send() to transmit an object to the child process. The child process listens for the message event and responds with its own message using process.send(). Both sides can handle complex objects, not just strings, making IPC a powerful tool for building scalable applications.

IPC channels are especially useful in real-world scenarios where you need to coordinate work between multiple processes, such as distributing computationally intensive tasks, managing worker pools, or keeping services in sync. By using message passing, you can design robust workflows that take full advantage of Node.js's non-blocking architecture.