Introducing Karma, we talked about PhantomJS and its usage as a virtual browser during unit testing execution. More precisely, PhantomJS (http://phantomjs.org/) is a headless WebKit scriptable browser, which means that:
It's based on the well-known WebKit web engine
It downloads a web page from a URL, renders the content into the DOM, executes JavaScript if present, and the executed result will be reflected on the browser's DOM
It doesn't render the page into a visualized content
The term scriptable means that we can instrument a PhantomJS instance to do actions using a JavaScript API
PhantomJS is not related in any way to NodeJS and its plugin ecosystem: it's a simple cross-platform executable (can be installed on Windows, Mac, and Linux) that runs independently from other runtime engines.
Most common PhantomJS uses are (from PhantomJS website):
Headless web testing: Run functional tests with frameworks such as Jasmine
Screen capture: Programmatically capture...