Node.js is an event based, asynchronous I/O framework that runs on top of Google's V8 JavaScript engine.
Node.js - or just Node as it's commonly called - is used for developing applications that make heavy use of the ability to run JavaScript both on the client, as well as on server side and therefore benefit from the re-usability of code and the lack of context switching.
It's also possible to use majored JavaScript frameworks like YUI and jQuery for server side DOM manipulation.
To ease the development of complex JavaScript further, Node.js supports the CommonJS standard that allows for modularized development and the distribution of software in packages via the Node Package Manager.
Applications that can be written using Node.js include (but are not limited to):
- Static file servers
- Web Application frameworks
- Messaging middle ware
- Servers for HTML5 multi player games