Worker Threads in Node.js enable true multithreading by allowing JavaScript code to run in parallel, which is essential for handling CPU-intensive tasks without blocking the main event loop. This guide covers the implementation, use cases, communication methods, and best practices for using worker threads effectively in production applications. It also emphasizes the importance of security and performance considerations when utilizing this feature.

The author discusses the importance of parallelisation as a fifth type of optimisation in programming, highlighting its benefits through personal experiences with website building and testing frameworks. They reflect on the historical limitations of hardware and programming languages that hindered effective parallelisation, while emphasizing the advancements in multicore CPUs that have made it more accessible and beneficial for boosting performance and productivity.