Node.js is a JavaScript runtime built on Chrome’s V8 JavaScript engine. It allows developers to run JavaScript on the server side, which can be used to build scalable and efficient network applications.

Node.js is based on an event-driven, non-blocking I/O model, which makes it well-suited for building real-time applications that require high levels of concurrency. It is also designed to be lightweight and efficient, making it a good choice for building applications that need to handle large amounts of data or traffic.

Node.js includes a number of built-in libraries for common tasks such as networking, file system access, and cryptography, as well as a package manager (npm) for installing and managing third-party packages.

Node.js is widely used for building web servers, APIs, and other types of networked applications. It is popular due to its high performance, ease of use, and the large and active community of developers that contribute to the platform.