Node.js provides a single-threaded JavaScript run-time surface that prevents code from running multiple operations in parallel, but it uses a separate pool of threads for I/O operations. The `worker_threads` module allows developers to create independent threads within their Node.js application, enabling parallelism and potential performance improvements. Worker threads are not true threads, but rather distinct processes that can communicate with the main thread using an event-based messaging system. They can be used for CPU-bound operations such as image resizing, video compression, and file encryption, while I/O-bound tasks should be handled by Node.js's built-in async utilities. The `worker_threads` module provides a convenient mechanism for running code in parallel, making it suitable for applications that require intensive work outside the main loop.