Node.js 9 is available to download now, as announced by Node.js foundation. You can download the latest version of Node.js 9.0.0 here from the foundation website: https://nodejs.org/
Node.js is a server-side JavaScript platform which is built on Google Chrome’s JavaScript V8 engine. It is an open source and cross-platform application to develop server-side and networking applications. Anyone can develop the Node.js application by writing code in JavaScript and it can be run on Microsoft Windows, Linux or OS X.
Node.js is not a new language and also it is not just a framework built on JavaScript. It is built on Chrome's JavaScript Runtime, so the code is written and executed similarly to the browser.
To learn more about Node.js, start here: