Node.js is an event-driven runtime environment for JavaScript that provides a way to run JavaScript code on the server-side of the browser/server relationship. It uses the V8 engine and offers concurrency models, HTTP support, and support for asynchronous programming capabilities like callbacks and Promises. The source code is available on GitHub, and Node.js can be installed for free from the official website. Once installed, npm (the Node Package Manager) can be used to install add-on libraries that extend JavaScript functionality. Node.js has a minimal impact on system resources and can be run from the command line with the `node` executable. To get started with Node.js, one should first understand its purpose and how it works, as well as learn about concurrency models and asynchronous programming capabilities.