RingoJS is a server-side JavaScript runtime built on the Java Virtual Machine (JVM). Unlike Node.js, which is based on Chrome's V8 engine, RingoJS leverages the stability and multithreading capabilities of the JVM. It implements the CommonJS specification for modules, making it easy to structure large applications. RingoJS is particularly well-suited for enterprise environments where Java infrastructure is already in place, as it allows seamless integration with existing Java libraries and concurrency models using Java's threading rather than JavaScript's event loop. While less popular than Node.js, RingoJS offers a robust alternative for developers seeking JVM performance and true multi-core processing out of the box.