Node.js is a runtime environment that allows JavaScript to run outside a web browser. Built on the V8 JavaScript engine, it enables developers to create backend services, command-line tools, and automation scripts. This makes it possible to use JavaScript for both frontend and backend development.

One of Node.js’s main strengths is its asynchronous, event-driven approach. It can handle tasks such as reading files and communicating with databases without blocking the main execution thread while waiting for results. This makes it well suited to applications that manage many simultaneous input and output operations.

Node.js provides built-in modules for working with files, networking, and other system features. Developers can extend its capabilities through packages distributed using npm. Frameworks such as Express help organize routes, middleware, and request handling when building web servers and REST APIs.

Node.js can connect to databases such as MongoDB and PostgreSQL and support features including authentication, payment processing, and real-time communication. However, CPU-intensive work can block its event loop unless handled appropriately, such as through worker threads or separate services. Understanding these strengths and limitations helps developers build responsive, maintainable applications.