node-sass is a library that provides binding for Node.js to LibSass, the popular Sass compiler. It allows developers to compile .scss files to .css directly from their Node.js applications. It's widely used in build processes and task runners like Gulp and Grunt, enabling seamless integration of Sass compilation into development workflows. node-sass offers performance benefits by leveraging LibSass's speed and provides access to the full power of the Sass preprocessor within the Node.js ecosystem.