Node.js
Node.js is an open-source, cross-platform JavaScript runtime environment that executes JavaScript code outside a web browser. It uses an event-driven, non-blocking I/O model, making it efficient for building scalable network applications, particularly server-side web applications and APIs. It is built on Chrome's V8 JavaScript engine and includes a rich ecosystem of packages via npm (Node Package Manager).
Developers should learn Node.js for building fast, scalable server-side applications, real-time applications like chat apps or gaming servers, and microservices architectures. It is ideal when using JavaScript across the full stack (e.g., with React or Angular on the frontend), as it allows code reuse and simplifies development. Node.js is also commonly used for tools like build systems, DevOps scripts, and IoT applications due to its lightweight nature and extensive package library.