Node.js is like JavaScript’s cool cousin that lives on the server-side. It’s an open-source, cross-platform runtime environment that allows developers to use JavaScript for server-side scripting. This means you can build the backend of an application entirely in JavaScript, creating a more unified and streamlined development process. Node.js is known for its non-blocking, event-driven architecture, making it perfect for real-time applications like chat apps, online gaming, and live streaming. Think of Node.js as the key that unlocks the full potential of JavaScript beyond just web browsers.